Abstract: OBJECTIVE To investigate the effect of valsartan on abnormal glycosylation of serum IgA1 in rats with IgA nephropathy(IgAN). METHODS SD rats were randomly divided into normal group, IgAN group, valsartan group, and prednisone group, with 12 rats in each group. IgAN rats induced by oral administration of bovine serum albumin(BSA) and intravenous staphyloentero-Toxin (SEB) by turns. The valsartan group were treated by oral valsartan 30 mg·kg^-1·d^-1 and prednisone group by oral pred 5 mg·kg^-1·d^-1. The 24 h urinary protein excretion(UPE) were measured in the first, 8th, 12th week respectively. Rats were sacrificed at 12th week. Serum IgA was measured with ELISA method and abnormal glycosylated IgA was measured with lectin affinity ELISA method. The kidney sections by kinds of staining were observed for renal pathological change of the rats in each group. RESULTS Compared with normal group at 8th week, UPE increased significantly in IgAN group, valsartan group and prednisone group. UPE decreased significantly in valsartarn group and prednisone group compared with IgAN group at 12th week. The serum IgA in valsartan group and prednisone group decreased significantly compared with IgA group. Pathological injury such as glomerular capillary occlusion, increased mesangial matrix, mesangial cell proliferating, IgA deposition and electron-dense deposits in mesangial area were mitigated in valsartan group and prednisone group compared with IgAN group. Compared with normal group abnormal glycosylated IgA1 increased significantly in IgAN group but were extenuated in valsartan group. Abnormal glycosylated IgA were not ameliorated in prednisone group with respect to IgAN group. CONCLUSION Valsartan can decrease serum IgA and ameliorate abnormal glycosylation of IgA to improve the outcome of IgAN. It may be an important mechanism of valsartan to treat IgA nephropathy.