The electrical potential difference (PD) was measured across the wall of reverted intestinal sacs. The effect of the effective component of Rhubarb on transmural potential related to Na+ and glucose transport were investigated. It was found that total glucoside of Rhubarb, Emodin and Sen-nosides decreased the PD. The experimental resuilts provide new scientific basis for explaining the mechanism of Rhubarb's purgative action.