AbstractWetland ecosystem is the living and breeding area of fish. Because its special location , the study and conservation of fish diversity of Yunnan are very important not only for China , but for neighboring districts and countries. So it should be paid great attention by biologists and conservation organizations. There are many characteristics in fish fauna of Yunnan , such as abundant species and endemic species , complex fauna and diverse species types and small population size. The following factors affect fish living and breeding : habitats damaged by reclaiming land from lakes and swamping , competition for space and food from introduced species , worsening environment quality by pollution , population decrease or extinction resulted from over-fishing , water environment changes by dam and power station , influence from water resources exhaustion and forest declination. All groups of living things and the internal extinctive mechanism of fish species should be studied for conserving organisms in wetland ecosystem. The law of species introduction should be legislated immediately.