Benthic Integrity Biotic Index (B-IBI) was used to evaluate the health of inflow rivers in Lake Dianchi of Yunnan Province, China.Macroinvertebrate assemblages were collected from 38 sampling sites in Lake Dianchi,including 9 sites that were undisturbed or less disturbed and 29 sites that were disturbed in wet season of July-Aug.2009 and dry season of Jan.-Feb.2010.The range of index value distribution,spearman correlation and judgment ability were analyzed for the 19 biological parameters,including Shannon-Wiener index;total number of taxa;total density;taxa numbers of Crustacea+Mollusca,Hirudinea,and Mollusca taxa;percentage of Crustacea+Mollusca,Hirudinea,Mollusca,Oligochaeta,Limnodrilushoffmeisteri,Chironomidae,Oligochaeta/Hirudinea,Gatherers,Predator,Omnivore,and Scrapers;percentage of tolerant taxa;and Goodnight index.Ratio scoring method for B-IBI index was used to get a uniform score.By using the each 20 percentiles of B-IBI as a criteria to evaluate the aquatic ecosystem health,the results showed that,health criteria when B-IBI > 1.62,sub-health when 1.03 1.62,good-fair when 0.31-1.03,fair when 0.10-0.31,and poor when B-IBI < 0.10.The B-IBI index was positive correlation to NO-3-N and water temperature,but not significantly correlation to other factors.