To study the function of expelling water retention with drastic purgation of Jingdaji（Euphorbiae Pekinensis Radix，EPR）before and after being processed with vinegar on cancerous ascitesmodel rats.

Seventy-two SD male rats were random ly divided into 9 groups：the normal group，model group，positive group（furosemide），EPR and vinegar product groups at low，medium and high dose.Except the normal group，all other groups had intraperitoneal injection with Walker-256 ratascites cancer cells to replicate cancerous ascitesmodel rats.Positive group and each administration groups were orally administered with the corresponding powder，respectively.Normal group and model group were given the same amount of sodium carboxymethyl cellulose（0.5%）for 7 d.1 hour after the lastadministration，the amount of urine and ascites，and the contents of the renin-angiotensin-aldosterone system（RAAS）and antidiuretic hormones（ADH）in the serum were measured.Liver and kidney function indicators，oxidative damage indicators and pathological morphological changes in liver，stomach，intestine and kidney tissues were observed.

Compared with the normal group，the model group showed a significant decrease in urine output and a significant increase in ascites volume（P<0.01），which indicated themodelwas successfully set up.The levels of plasma renin activity（PRA），angiotensinⅡ（AngⅡ），aldosterone（ALD），ADH，creatinine（CRE），blood urea nitrogen（BUN）and the activities of aspartate aminotransferase（AST），alanine aminotransferase（ALT）and malondialdehyde（MDA）in the serum and tissues all significantly increased（P<0.01），while the contents of superoxide dismutase（SOD）and glutathione（GSH）were significantly decreased（P<0.01），also there were obvious tissue damage in liver，stomach，intestine and kidney.Compared with those in themodel group，the urine volume in each administration groups increased，ascites volume，the levels of PRA，AngⅡ，ALD，ADH，CRE and BUN，the activities of AST and ALT and the content of MDA in the serum and tissues decreased，and the contents of SOD and GSH increased.The injury of each administration groups reduced，and there was no significant difference between EPR raw and vinegar-processed product powders.

EPR before and after processing with vinegar have the effects of expelling water retention with drastic purgation，by stimulating the RAAS to eliminate ascites and alleviate oxidative damage of cancerous as cites model rats.