Trịnh Cương ruled Việt Nam during a time of external peace but growing internal strife. He enacted many governmental reforms in both financial matters and judicial rules. His main concern was the growing problem of landless peasants. Unlike the Nguyễn lords who were constantly expanding their territory south, the Trịnh lords had little room for expansion. Hence, the land supply was essentially fixed but the population kept growing.
Trịnh Cương tried various legislative means to solve the problem. He tried to limit private land holdings. He tried to redistribute the communal fields of the small villages. Nothing really worked and the problem became very serious over the succeeding decades. According to historian R. H. Bruce Lockhart, the governmental reforms enacted by Trịnh Cương and his great-grandfather, Trịnh Căn, made the government more effective but, they also made the government more of a burden to the people. This had the effect of increasing the hatred felt by the people towards the Trịnh rulers in Hanoi.
Trịnh Cương passed an edict forbidding people to practice Christianity in 1712. Like previous efforts to suppress Christianity, this had little real effect in Vietnam. However, he tried to offer the people an alternative, and he had many Buddhist pagodas constructed during his rule.
As far as the Lê dynasty was concerned, the emperor, Lê Dụ Tông, ruled throughout Trịnh Cương's lifetime. The two men died within a few months of each other in 1729.
