Using the hemal spine and anal fin as morphology indicator, mosquitofish living in Haizhu Creek and Huangpu Creek were sampled and detected in order to assess the endocrine disrupting effects. We measured the 4,5,6 anal strip length and the third section rays scores, and used the 14th, 15th, 16th hemal spine and L, P, D, L/D ratios, P/D ratios, P/L ratios as indicator to assess the modification of skeletal morphology. The results showed that higher number of the 3rd anal fin ray and the increased ray 4:6 length ratio were observed in mosquitofish sampled in the Haizhu River and Huangpu River. The adult female mosquitofish exposed to municipal effluent had significantly greater in 14P, 15P and 16P than those at reference site. The ratios of 14P:14D, 15P:15D and 16P:16D of adult females were found to be significantly increased in Haizhu River and Huangpu River. Female mosquitofish in Haizhu River and Huangpu River exhibited signs of male-like hemal spine development. However there were no differences between male mosquitofish from test and the reference site. The results indicated that the environmental endocrine disruptors in water of Guangzhou Creek could produce the effect of morphological masculinization in female mosquitofish.