In this study, Schizandriae fructus which has been used in oriental medicine and folks remedy, was studied to apply to functional foods and oriental medicinal cuisine. The aim of this experiments was to investigate the effects of Schizandriae fructus water extract(SFE) on the renal function, plasma renin activity, plasma levels of aldosterone and arterial natriuretic peptide(ANP) in rats. Spargue-Dawley rats weigh 200g, were randomly assigned to 3 groups such as basal diet only(BDG), basal diet with $0.5{mu}L/g$ SFE(LAG) and basal diet with $1.0{mu}L/g$ SFE(HAG). The results were as follows. Water balance decreased significantly after administration for 2 weeks compared with the control period in HAG. Urine volume increased significantly after administration for 1 week compared with the control period in LAG and HAG. Urinary excretion of sodium increased significantly after administration for 1 week and for 2 weeks compared with the control period in LAG and HAG. Urinary excretion of creatinine increased significantly after administration for 2 weeks compared with the control period in HAG. Plama levels of ANL decreased significantly after administration of $SFE(0.5{mu}L/g)$. Plasma levels of aldosterone decreased significantly after administration of $SFE(1.0{mu}L/g)$. There results indicated that Schizandriae fructus can improve the renal function through increased urine volume and sodium excretion. These results imply that SFE could be used as a potent food resource for diet therapy or clinical nutrition.