Abstract: The high flow pulse process is a key eco-hydrological indicator for the spawning of drift egg laying fish. In order to promote the rare and unique fish species spawning in the National Nature Reserve for rare and endemic fishes in the upper reaches of the Yangtze river and explore the conditions for ecological operation of cascade reservoirs in the lower Jinsha River, a analysis of the composition of runoff in the National Nature Reserve during drifting egg fish spawning was conducted. The contribution ratio of the upstream main and tributary streams flow to the formation of high flow pulses in National Nature Reserve was evaluated, and the close relationship between the spawning situation of Coreius and Leptobotia elongate and the high flow pulse of main and tributary streams was analyzed. The results showed that half of high flow pulses in the National Nature Reserve are formed by the jiont flow rise of tributary streams and Jinsha River, while the other half are formed alone by the flow rise of tributary streams. The contribution ratio of the tributary streams flow to the formation of high flow pulses in National Nature Reserve during the high-flow pulses is as high as 87.62%.The spawning of representative fish species mostly occurs during the period when high-flow pulses appear in tributary streams.The flow rise process of tributary streams plays a key role in the formation of high flow pulses in the National Nature Reserve.The cascade reservoirs in the lower Jinsha River should carry out ecological compensation operation in conjunction with the flow rising process of tributary streams, which will be beneficial for fish spawning and reproduction in the National Nature Reserve, and also reduce the artificial flood peak pressure of the cascade reservoirs in the lower Jinsha River.