Abstract: OBJECTIVE To investigate the effects of phytolaccae radix before and after vinegar processing on diuretic effects and related factors. METHODS Saline-loaded model rats were given different kinds of phytolaccae radix decoction by gavage to detect the changes of urine volume within 5 h， plasma concentrations of ADH， ALD， ANP and protein expression levels of AQP2， AQP3 and AQP4. RESULTS Phytolaccae radix before and after vinegar processing significantly increased the urine volumes of rats (P<0.01) and vinegar product significantly increased urine volume compared to raw product (P<0.05). Only high dose of raw product significantly reduced plasma concentration of ADH (P<0.01) and caused a tendency to reduce ALD and increase ANP content， without significant difference. Vinegar product significantly reduced plasma concentrations of ADH， ALD and increased ANP content (P<0.05， P<0.01). Raw product significantly inhibited the protein expressions of AQP2， AQP3 and AQP4 (P<0.05， P<0.01) while vinegar product significantly inhibited the protein expressions of AQP2 and AQP3 (P<0.01)， whereas showed no significant influence on AQP4 protein expression， compared to control group. Moreover， vinegar product inhibited the protein expression of AQP3 more significantly than raw product (P<0.05). CONCLUSION Phytolaccae radix after vinegar processing still retains diuretic effect and its efficacy is better than that of raw product at the molecular levels. The diuretic mechanism of phytolaccae radix maybe associated with changing hormone levels of fluid metabolism， and the inhibition of AQPs protein expressions in renal distal convoluted tubules and collecting ducts， which can inhibit water reabsorption.