Abstract: To better guide the rational development and sustainable utilization of water resources, the hydrological method was used to determine the ecological flow of the main stream and important tributaries of the Ganjiang River, and the available surface water resources in each sub-region was quantitatively evaluated.The results show that:(1) The ecological flow of each section of Ganjiang River is 44.8～281m3/s, accounting for 11.7%～13.6% of the annual flow, while that of tributaries is 6.03～19.80 m3/s, accounting for 9.4%～10%of the annual flow.The average daily flow satisfaction of each section in the past 10 years is above 92%,which can be used as the basis for ecological flow control.(2) The annual average available surface water resources in the Ganjiang River Basin above Waizhou is 22.42 billion m3 with the availability of 29.6%,while that in each major tributary is 0.71～2.21 billion m3 with the availability of 19.7%～29.3%.The water resources availability in the downstream is generally higher than that in the middle and upper reaches.With the improvement of the efficient utilization of flood resources, water resources availability can be further increased.The results can provide a reference for guiding the water distribution and scheduling in the watershed, and strengthening the development, utilization and protection of water resources.