Abstract: Discharge from 1961 to 2099 through the outlet of Xijiang River, the biggest sub-basin of Zhujiang River, was simulated by hydrological model HBV-D using the precipitation and temperature projected from three climate models (GCMs) under three greenhouse gas (GHG) emission scenarios. The following conclusions can be drawn through analyzing the changes of water resources and flood frequency relative to the reference period of 1961-1990. Annual precipitation and annual runoff will increase after 2050. In addition, Area average precipitation and runoff show increasing trends in each month from May to October, but decreasing trends from December to next February based on the results of Mann-Kendall trend analysis. More and larger floods will occur in future. Potential increased runoff during the low flow season before 2030 will ease the pressure of water demand, but the increased runoff in the high flow season, and more frequent and larger floods will bring more pressure on flood controlling after 2050. These impacts of climate change on hydrological processes in the Zhujiang River basin should be considered when planning adaptation and mitigation strategies.