Objective: To explore the effect of the Nephritis No. 3 (N-3) recipe on nitric oxide (NO),nitric oxide synthase (NOS) secreted by cultured mesangial cells (MC) and its gene expression of the inducible nitric oxide synthase (iNOS). Methods: The drug (nephritis No. 3)-containing serum was prepared with serum pharmacological technique, and then was applied to react on mesangial cells cultured in fetal calf serum (FCS) and cells cultured in FCS plus lipopolysaccharide. To observe the secretion of NO and NOS and the gene expression of iNOS by means of RT-PCR. Results: Under the two kinds of culture conditions, the content of NO and NOS in the groups with drug-containing serum were higher than those without drug-containing serum (P＜0.05, P＜0.01), and the expression of iNOS mRNA was up-regulated too. Conclusion: The N-3 could significantly promote the secretion of NO and NOS and the mRNA expression of iNOS in rats.