Abstract: Based on the data from the first to ninth forest inventories from 1973 to 2018, this study analyzed the patterns of changes in forest resources in terms of cover and age group structure. According to the situation of forest resources and population in China, the suitable forest coverage rate was studied. In response to the problem of young age groups of forest resources, an age group optimization model was constructed, the age group structure was optimized, and development suggestions were made. The results show that China's forest cover is steadily increasing, but the area of suitable land for forest has decreased, the age-group balance ratio of forest resources in all periods is lower than 0.8, and the age-group structure is extremely uncoordinated. According to the standard of 0.16 hm² per capita forest area in the 9^th forest resource inventory, the suitable forest coverage rate in China was 25.89%, and only 15 of 31 provinces reached the standard of per capita forest area. The ideal age-group ratio of China's forests were 16.00% in young forest, 21.33% in middle forest, 16.00% in near mature forest, 30.67% in mature forest and 16.00% in overmature forest. The age group optimization model constructed in this study can regulate the age groups to tend to balance, and the adjusted age group balance rate can reach 0.85. The theory and results of this model can provide reference for forest resource management in China.