In this paper the main reason of the extinction M.reevesii was established. The fact is that the stepped hydropower station have changed the original environmental, conditions of Qiantangjiang River especially the conditions of Xin'anjiang River resexvoir and Hunanzhen reservoir,from which the temperature of annual reservoir water exchange values are 0.6 and 1.3 respectively and the sluiced cold water is 10℃ , thus the natural environmental conditions of the limited water temperature fox Macrura reevesii were destroyed.The research of this project has provided a scientific basis for expounding the natural characteristics of Macrura reevesii as well as the countermeasures to the project. Introducing cold-water fish species or wide temperature character fish species would be an effective way of rebuilding the fishery resources.