Zhang started to play aged 8, influenced by his father, who was a club-level player. He had seen Ding Junhui playing on television, and expressed an interest. At the age of 11, Zhang left mainstream school and went alone to Shenzhen and later Shanghai, where he was coached by Wu Wenzhong who had previously coached Ding Junhui. In 2014 Zhang won the Sichuan Provincial Championship and the Chinese U21 Championship, and was accepted in the CBSA Academy in Beijing.
Following Zhang's promising performances in the academy and in Chinese tour events, the CBSA awarded him a wildcard for the 2016 International Championship in Daqing. There he defeated Ross Muir 6-3 before losing to Stuart Bingham 6–1.
In April 2018 he was awarded a two-year professional tour card, being ranked at the highest amateur in the CBSA China Tour ranking list. Ahead of the 2018–19 season he has been announced as being based at Q House Snooker Academy in Darlington as a resident professional, managed by Chusak Phetmalaikul.
He competed at the 2018 World Snooker Team Cup representing China with Fan Zhengyi but they lost to India 2–3 in the Round of 16.
Zhang's first win as a professional was against Michael Holt in the European Masters. Unfortunately, a lost ID card meant he was unable to travel to the UK to compete in the World Championship. He finished his first season ranked 113.
At the start of the 2019–20 season, Zhang was again affected by travel problems, missing the first two tournaments. He then went on a losing run of 5 matches. At the Scottish Open he produced his best performance to date, beating Chen Feilong, John Astley and Tom Ford to reach the last-16, where he lost to Scott Donaldson. In the Welsh Open he lost 4–1 in the first round to 5-times World Champion Ronnie O'Sullivan.
With the outbreak of COVID-19, Zhang sought to return to China on 29 March. His journey included quarantines in both Shanghai and his hometown Yibin, after an internal flight. He finally reached home after almost 1 month of travelling. On 28 June it was announced that he would not be returning to the UK for the World Championship, which had been rescheduled for July. This confirmed his relegation from the tour, being ranked outside the top 64.
The 2020-21 season was severely disrupted by the COVID-19 pandemic. The first snooker tournament to be staged was a teams event in Lanzhou in November 2020. Zhang Jiankang played for the Sichuan team, but they lost in the last-16 to the Jilin team. In April 2021, there were two tournaments in Beijing to determine 4 qualifiers for the World Professional Tour for the 2021-22 season. With wins over Wi Ning, Lin Hui, Fang Xiongman, Ju Reti and Deng Haohui, Zhang successfully progressed from the first event, losing only 4 frames in his six matches.
In June, the China City teams event was staged, also in Xi'an. Most of the top players in China participated in the 35-team event, including 15 professionals. Zhang Jiankang played for the Sichuan team, alongside Zhou Yuelong and Cai Wei. Zhang scored the first century break in the competition, 115 against Dalian. Sichuan topped their group, and proceeded to the knockout phase. In the Q-final Zhang won a tense deciding frame against Cao Yupeng of Suzhou, the tournament favourites. But ultimately Sichuan lost 4-2 in the final to Shanghai, whose players were Tian Pengfei, Lu Ning and Zhao Jianbo.
Performance and rankings timeline
|Northern Ireland Open||A||A||1R||1R|
|World Grand Prix||DNQ||DNQ||DNQ||DNQ|
|Tour Championship||Not Held||DNQ||DNQ|
|Former ranking tournaments|
|Paul Hunter Classic||A||A||2R||NR|
|Performance Table Legend|
|LQ||lost in the qualifying draw||#R||lost in the early rounds of the tournament
(WR = Wildcard round, RR = Round robin)
|QF||lost in the quarter-finals|
|SF||lost in the semi-finals||F||lost in the final||W||won the tournament|
|DNQ||did not qualify for the tournament||A||did not participate in the tournament||WD||withdrew from the tournament|
|NH / Not Held||means an event was not held.|
|NR / Non-Ranking Event||means an event is/was no longer a ranking event.|
|R / Ranking Event||means an event is/was a ranking event.|
|MR / Minor-Ranking Event||means an event is/was a minor-ranking event.|
|VF / Variant Format Event||means an event is/was a variant format event.|
- It shows the ranking at the beginning of the season.
- He was an amateur.
- New players on the Main Tour don't have a ranking.
- Pathak, Vivek. "China rocks with five centuries before knockout qualification; Zhang missed the MAXIMUM". IBSF.
- News, Blasting. "QSchool Snooker: Who's hunting for a tour place?".
- "Q House Snooker on Twitter".
- "World Snooker Team Cup: India in Doha semis - The Peninsula Qatar". www.thepeninsulaqatar.com.
- "12 Chinese Players to Miss World Championship".
- "Coronavirus: World Snooker Championship at Crucible postponed". BBC Sport. 20 March 2020. Archived from the original on 24 March 2020. Retrieved 20 March 2020.
- "Ranking History". Snooker.org. Retrieved 6 February 2011.