Objective To investigate the effect of chronic intermittent hypoxia (CIH) on renal ultrastructure and function in immature rats. Methods A total of 22 postnatal day 21 (P21) Sprague-Dawley (SD) male rats were randomly averagely divided into two groups:control group and CIH group.CIH-handled rats were exposed to intermittent hypoxia in designed cabin 8 hours every day,and the duration of hypoxia was 6 weeks.The renal ultrastructure was observed by transmission electron microscopy.The value of serum malondialdehyde (MDA) and renal malondialdehyde,activity of urinary enzyme N-β-D-glucosaminidase as well as content of the urinary creatinine were detected by colorimetry. Results The renal ultrastructure of control group were normal.The glomerular endothelial cells showed edema and the foot process fusion were demonstrated in CIH group.Renal tubular epithelial cells appeared obvious edema in CIH group.Compared with the control group,the value of serum MDA and renal MDA were increased obviously (P<0.01).There were significantly increased in activity of Urinary N-acetyl-D-glucosaminidase (NAG) of CIH group (P<0.01),but the content of the urinary creatinine were less than those in control group (P<0.05). Conclusion The study demonstrated CIH exposures result in changes of renal ultrastructure and impairment of renal function,which may be associated with the produce of excessive oxygen radicals after hypoxia.