Objective To investigate the changes of kidney weight and histological structure，activities of superoxide dismutase(SOD)，catalase(CAT) and content of maleic dialdehyde(MDA) in kidney after the developing filial mice received intragastric administration of melamine, and to evaluate the effects of melamine on kidney development of filial mice．Methods Totally 160 filial mice at the seventh day respectively received 0.3，0.8 and 1.3g/(kgI>&#/I>8226;d) doses of melamine in the three experimental groups by intragastric administration，while the control group were given the same amount of saline．The samples were harvested at day 6，12，18，24 and 30 respectively． The shape and weight of kidneys were determinded，and the activities of SOD，CAT as well as content of MDA were detected by colorimetry．In addition，the changes of the renal lesions were observerd by optical microscope in all groups．Results At day 18-30 after the administration of melamine， kidneys of some experimental filial mice were swelling with reddish brown appearance，and the body weights were significantly higher than those of the control group．In 0.3g/(kgI>&#/I>8226;d) and 0.8g/(kgI>&#/I>8226;d) group，SOD and CAT activities in kidney increased and were higher than that of the control group in the early time，then decreased and were significantly lower than that of the control group after 24 days， while MDA content in kidney decreased and lower than that of the control group in the early time，then increased and much higher than that of the control group after 24 days. In 1.3g/(kgI>&#/I>8226;d) group, SOD and CAT activities in kidney were always significantly lower than that of the control group，and MDA content was always much higher than that of the control group．With the extension of administration days，cortex and medulla of kidney of experimental filial mice appeared with some difference．The epithelial cells of renal tubule and collecting duct were swelling，vacuolization and necrosis；expansion and hemorrhage of capillary；colloid-like material appeared