2008

Deng made her international competitive debut in 2008, when she competed in several events on the World Cup circuit. At the World Cup meet in Doha in March, she won the gold medal on the balance beam and placed second on floor exercise behind her teammate Jiang Yuyuan.^[3] At the World Cup in Moscow, Deng won gold medals on both beam and floor.^[4]

At the 2008 Chinese National Championships, Deng finished in third place in the all-around, behind Jiang Yuyuan and Yang Yilin^[5] and also placed third on vault.^[6]

2009

In 2009, after a seven-month-long knee recovery, Deng started to prepare for the 11th Chinese National Games held in September. During the competition, she surprisingly won the gold in the all-around final from the second group (7th in qualification) of the 24 finalists. After posting three solid routine on bars, beam and floor, she took a shot on vault by attempting the double twisting Yurchenko and succeeded with a clean landing to guarantee the win over Yang Yilin and Sui Lu from Guangdong and Shanghai, respectively. In the floor final, she got a bronze medal with a clean but relatively simple routine.

Later the same month, she became the world champion on balance beam in London. During the beam event final, she obtained the highest values in both D and E scores with 6.4 and 8.6, respectively. She became the fourth beam world champion of Chinese team, after Mo Huilan, Ling Jie and Fan Ye. In addition, she finished seventh on the floor exercise and eleventh in the all-around competition, after an uncharacteristic fall on her own strong event, balance beam.

2010

Deng struggled with her sciatic injury throughout 2010, which forced her to only compete on vault and beam. Even so, she continued her international success in 2010, garnering a team bronze medal at the 2010 World Championships with the Chinese team as well as an individual silver medal in the balance beam final. During the team final, the judges devalued her back layout somersault (an E level element) to a whip (a C level element), which resulted her 0.7 valued back flip + back flip + back layout series to only a 0.3, and the shown 15.10 score replaced with 14.70 after a call made from the Russian senior judge. In the beam final, she held the highest D value, a 6.6, of all the competitors. She was also chosen to compete in the 2010 Asian Games, where she won a gold with the team and an individual silver on the balance beam behind her teammate, Sui Lu.

2011

In 2011, Deng did not make the team for the 2011 World Championships in Tokyo due to injury. In November, she won an all-round title in the Chinese Winner Champions held in Hong Kong over her younger teammates. During this competition, she performed a 1.1 valued series of back flip + back flip + layout full (G level) + Korbut flip, which included a 0.4 connective bonus value; under AB/DE COPS, this is the highest value generated by one move on beam.

2012

In 2012, despite injuries, Deng regained the ability to vault a double twisting Yurchenko which was urgently needed for the Chinese team. With the winning of the all-around title at the Chinese National Championships, Deng made herself a member of the Chinese gymnastic team going to the 2012 Olympic Games. Due to Deng being declared the fourth member of the team, her long term teammate He Kexin was chosen as the final member because of her bars specialty.