Abstract: The study of waters ecosystem and their population carrying capacity demonstrates the role of these ecosystems in economic and social development and provides a theoretical basis for the management and allocation of aquatic ecosystems. In this study, the concept of waters ecosystem population carrying capacity was defined and developmental trends in the population carrying capacity of waters ecosystem in China were evaluated. Results show that waters ecosystem population carrying capacity in China increased from 0.176×10⁹ person year^-1 in 2000 to 0.255 ×10⁹ person year^-1 in 2010; the population carrying capacity of the standard sea remained at 0.2-0.3 person ha^-1; and the standard inland waters population carrying capacity increased from 1.8 to 3.2 person ha^-1. This analysis indicates notable regional difference in waters population carrying capacity. In southeastern coastal China and Yangtze River drainage areas where inland waters are widely distributed and aquaculture is developed, the population carrying capacity is higher; however, in northwest China where water resource are deficient and the distribution is relatively small, the waters population carrying capacity is low. The waters ecosystem population carrying capacity of China in 2030 was predicted and results indicate strong potential for increasing waters population carrying capacity.