Abstract: Objectives To investigate the correlation between the variation of microcystin (MC)and environment factors in Tingxi Reservoir, Xiamen to provide a scientific basis for early warning and monitoring of MC.Methods The concentration of microcystin and main environment factors, including chlorophyll-a, total nitrogen, total phosphorus, ammonia-nitrogen, nitrate-nitrogen, permanganate index, 5-day biochemical oxygen demand (BOD₅), dissolved oxygen, secchi clairity, water temperature and pH were determined in 2009—2010 and evaluated according to the Environmental Quality Standards for Surface Water (GB 3838-2002). The correlation between MC and environment factors was performed with SPSS 19.0 statistical software.Results The trophic status of water in Tingxi Reservoir was from mesotrophic to light eutrophic. The detection rates of MC-LR and MC-RR were 43.48% and 56.52% and the detection value were in the range of 0.0025～0.238 μg/L and 0.0012～0.162 μg/L, respectively. The concentration of MC-RR was significantly negatively correlated with secchi clairity(P<0.05), but no significant correlations was found between MC and the rest of environmental factors.Conclusions The eutrophic level of water in Tingxi Reservoir was low. Multifactor stepwise regression analysis indicated that the main affected factors for the distribution of MC in Tingxi Reservoir were total nitrogen and secchi clairity(R²=0.419,P<0.006).