Abstract: This study is aimed to investigate the potential mutagenicity of tap water and their source water from water plants in Kunming with tadpole micronuclei and chromosomal aberrations (CA) and sister chromatid exchages (SCEs) tests of cultured CHO cells.The results revealed:1) There is an obvious difference on frequency of tadpole micronucleus induced between each water plant tap water and its source water with the exception of Y-water plant tap water.2) The results of CA frequency showed no substantial difference between each water plant tap water and its source water and control group except of low concentration (0.03125 L/ml) group of W-water plant tap water.3)There is an extremly significant difference between the high concentration groups 0.0625 L/ml (Dianchi Lake source water and W-water plant tap water),and low concentration group (W-water plant tap water through comparison with control group) with SCE frequency.There is a significant difference in low concentration group of Dianchi Lake source water and high concentration group of E-,S-water plant tap water.