To study the long-term development of water resources supply and demand in Tianjin City, based on the current situation, a system dynamics model for sustainable water resources development in Tianjin was established using system dynamics and hierarchical analysis method. Then the simulation results were compared with the historical data from 2012 to 2019, the results show that the absolute value of the relative error is less than 10%, so the proposed model is highly reliable, which can be used to predict the future development of water resources carrying capacity of Tianjin City. Four different scenarios, namely, status quo continuity (S1), integrated water conservation (S2), open-source and pollution control (S3), and integrated development (S4) were set in the system dynamics model to predict the situation of water supply and demand balance in the time frame of 2020-2035. The results show that the total water consumption in Tianjin can reach 4.158×109 m3 under scenario S1 in 2035, and the water resources carrying coefficients for scenarios S1-S4 in 2035 are predicted to be 0.178 2, 0.397 3, 0.481 5 and 0.728 1, respectively. The analysis shows that the water supply from the South-North Water Diversion Project East Line in 2025 will significantly alleviate the overload situation of water resources in Tianjin. Among the four development scenarios, scenario S4 has the best performance on alleviating the imbalance between water resources supply and demand, so the government should follow the principle of “prioritize water conservation and guarantee water supply”, and implement water conservation, pollution control, and open-source measures to ensure the sustainable development of water resources in Tianjin in the future.