[Objective] To explore the therapeutic mechanism of modified Zhuling Decoction (MZD) in treating primary mesangial proliferative glomerulonephritis (PMPG). [Methods] Rat models of PMPG were induced by rabbit type antibody of rat thymocyte (Thy-1). Forty rats were randomized into four groups: A (normal control), B (model), C (treated with heparin) and D (treated with MZD). Biochemical indexes in blood, activities of cytokines such as interleukin-1? (IL-1?), tumor necrosis factor ? (TNF-?) and interleukin-6 (IL-6) and mRNA expression of IL-6 were observed. [Results] As compared with group A, serum contents of IL-1?, TNF-? and IL-6 were increased and mRNA expression of IL-6 was promoted in group B (P