In view of the current severe situation of illegal land use in China, it is of great significance to explore the impact of the evolution and promotion of land law enforcement effectiveness, which will improve China’s land law enforcement system and effectively curb illegal land use. This paper explains the changes and enhancements of the effectiveness of land law enforcement since the implementation of China’s National Land Supervision System in terms of the deterrence, difficulty, and strength of land law enforcement, and explores the role of land law enforcement effectiveness in changing illegal land use behaviors from a theoretical level. Then, a corresponding empirical test was carried out using the provincial panel data of Mainland China from 2007 to 2016. The results show that the increase in land law enforcement deterrence and strength will help reduce the number of illegal land use cases, but it will drive the lawbreakers to "commit major cases in desperation", leading to the increase of the degree of illegal land use; and with the decrease of land law enforcement difficulty, the degree of illegal land use will be significantly reduced. At the end of this paper, several policy suggestions are put forward to effectively curb the illegal land use from the perspective of improving the land law enforcement system and enhancing the effectiveness of law enforcement.