Objective:To study the therapeutic effects and mechanism of Mahuang Lianqiao Chixiaodou Decoction in the treatment of IgA nephropathy in rats model. Methods60 male SD rats were divided into the normal group,model group,losartan potassium group, pseudoephedrine group and Mahuang Lianqiao Chixiaodou Decoction(Chinese medicine)group. Except the normal group, experimental IgA nephropathy model in SD rats was established by complex immunifaction of bovine serum albumin (BSA) plus lipopolysaccharide (LPS) plus carbon tetrachloride (CCl,4,) in the other groups. Each group was received the corresponding intervention. The changes of 24 hours protein quantitation, renal function and renal pathology in rats were observed, and the related cytokines were detected by ELISA and compared.  Results:①There was statistically significant difference on the level of urine protein between the model group and pseudoephedrine group or Chinese medicine group or losartan potassium group(P,<,0.05),which suggested that pseudoephedrine,Mahuang Lianqiao Chixiaodou Decoction and losartan potassium could significantly reduce proteinuria in rats with IgA nephropathy. ②There were statistically significant differences on the serum levels of creatinine(Scr) and urea nitrogen(BUN) between the model group and pseudoephedrine group or Chinese medicine group(P,<,0.05),which suggested that pseudoephedrine and Mahuang Lianqiao Chixiaodou Decoction could significantly reduce the serum level of Scr and BUN in rats with IgA nephropathy. ③There was statistically significant difference on the level of IL-21 between the model group and pseudoephedrine group or Chinese medicine group or losartan potassium group(P,<,0.05),which suggested that pseudoephedrine,Mahuang Lianqiao Chixiaodou Decoction and losartan potassium could significantly reduce the serum level of IL-21 in rats with IgA nephropathy. ④The mild hyperplasia in glomerular mesangial cells,eosinophilic changes in renal tubules and swelling in renal tubular epithelial cells were observed in the model group. The pathological changes were improved in the Chinese medicine group,losartan potassium group and pseudoephedrine group.  Conclusion:Mahuang Lianqiao Chixiaodou Decoction can significantly reduce proteinuria and serum levels of creatinine and urea nitrogen in rats with IgA nephropathy,and protect the renal function. Its mechanism is related to the decrease of serum IL-21 level in IgA nephropathy rats and the regulation of IL-21 involved immune response. Pseudoephedrine as the main effective components shows the same effects as this prescription.