Abstract: Microcystin (MC) is a common algal toxin in surface water and distributed widely in various types of water all around the world.It has confirmed that microcystin-LR did great harm to liver in human even under extremely low concentration.The contamination of Microcystin in source water and finished water has got increasing attraction.The current situation of microcystin contamination in source water and finished water in China and the correlation between MC and diseases was reviewed in this paper; the relationship of MC with environmental factors was also discussed, in order to provide constructive suggestions for monitoring and control of microcystin contamination in source water and finished water.