In order to broaden the adapibality of Tennant method,the paper proposed the determination method of ecological base flow in general period of using water (from November to next March) according to the feature of large difference between wet season and dry season; at the same time, in order to meet the survival and reproduction requirements of fish, the paper determined the required monthly minimum velocity in the fish-birth period (April to October) to select the larger flow which corresponding to the minimum flow velocity and traditional Tennant method ecological base flow as the final ecological base flow so as to safeguard the survival requirement of fish.Taking Xiaoqing River for example,the paper chose the historical data with less human interference to calculate the ecological base flow and verify it with the result of other calculation method. The results show that the improved Tennant method is more reasonable and takes into account the many aspects of water requirement.The method is helpful for the ecological protection and the sustained and healthy development of the river.