Forests play an important role in maintaining national ecological security, and urbanization has been an importantly strategic development plan in China. We should not only promote urbanization, but also improve the security of forest ecosystems. It is controversial whether urbanization in China will improve the security of forest ecosystem or worsen the forest ecological environment. The paper applies the PSR(Pressure-State-Response) model and EKC(Environment Kuznets Curve), uses the panel data of China's provinces from 1999 to 2018 to analyze the spatial and temporal variation of forest ecological security index. We establish a fixed effect model to study the impacts of urbanization in different periods and regions on forest ecological security in China. The conclusions are as follows. Firstly, from 1999 to 2018, the average forest ecological security index in China increased from 0.4683 to 0.5038, indicating that the forest ecological security level has been improved. Secondly, in the overall sample, there is an inverted U-shaped relationship between urbanization and forest ecological security index. When the level of urbanization is low, urbanization can improve the level of forest ecological security. On the contrary, urbanization can reduce the security of forest ecological security system. In addition, the impacts of urbanization on forest ecological security are temporal differences. From 1999 to 2010, there was a significantly positive correlation between urbanization and forest ecological security index, while from 2010 to 2018, there was a negative correlation between urbanization and forest ecological security index. Finally, there are regional differences in the impact of urbanization on forest ecological security. There is a significantly negative correlation between urbanization and forest ecological security index in eastern China, while there is a positive correlation between urbanization and forest ecological security index in central and western China. In addition, the ratio of tertiary and secondary industry is positively correlated with forest ecological security index, which indicates that the upgrading of industrial structure brings the improvement of forest ecological security. Based on the above analysis, the following suggestions are proposed:① we should accelerate the transfer of rural labor force to cities and encourage rural population to migrate to cities in areas with low urbanization level. We should strengthen the control of forest ecological security red line in areas with high urbanization level, and reduce total energy consumption and total pollution discharge. ② Green transformation of the industry and circular economy should be promoted under the guidance of the concept of ecological civilization.