The deterioration of cement paste exposed to artificial organic acid solution involved in biological metabolism and a scour of 2m/s was evaluated,in terms of the erosion depth,the decrease of calcium hydroxide content and the loss of mass per unit area of sample surface.The acceleration of deterioration of cement paste caused by the scour of solution was investigated by comparing to the deterioration under static immersion.The results show that ( 1) the erosion depth and the loss of mass per unit area of sample surface under the coupled effects of organic acids and scour are 2. 72 times and 3. 77 times those in static organic acid solutions,respectively; ( 2) the coupled effects of the organic acids and the scour significantly accelerate the deterioration of cement paste; and ( 3) the loss of mass per unit area of sample surface fully reflects the chemical erosion effect of the organic acids and the physical effect of the scour,meaning that this index is suitable to evaluate the deterioration of cement-based materials.