Objective To observe effect of different +Gz on renal function and its ultrastruture in rats.Methods Thirty-six male Wistar rats were randomly divided into six groups ( n =6 for each group).Group A served as ground control.Group B was exposed to +5 Gz while group C and group D exposed to +7 Gz, group E and group F exposed to +9Gz for 3 min in animal centrifuge (3 times,with 40 min interval in between).Blood samples of group B,C and group E were collected 6 h after +Gz exposure,and those of group D and group F collected 24 h after exposure,for the measurement of blood urea nitrogen (BUN), creatinine (Cr),alkaline phosphatase(AKP) and Ca 2+ levels. At the same time,the left kidney was taken for microscopic and electron microscopic examination.Results In comparision with group A, BUN in group C and group E were significantly elevated ( P <0.05). Ca 2+ levels in group B,C and group E were significantly decreased ( P <0.01, P <0.05 and P <0.01).AKP in group E was also significantly increased ( P <0.05).In electron microscopic examination, the pathological changes of mitochondria of glomeruli and renal tubules were found in rats after repeated +7 Gz and +9 Gz exposure.Conclusion Repeated +7 Gz and +9 Gz exposure may exert harmful effect on renal function and ultrastructure in rats.