Abstract: Objective To study the effect of first oral magnesium sulphate volume on intestinal preparation and satisfaction of patients. Methods Four hundred and fourteen patients were randomly divided into control group（group 1）,convention groups 2 and 3（138 in each group）.Patients in control group were given 70ml 50% magnesium sulfate immediately after taking 300ml water in 5 minutes.The patients were then given the remaining 1 200ml water after the first defecation and took a fast walk each time after drinking water.They could massage their abdomen on bed when they felt tired.Patients in convention groups 2 and 3 received 500ml and 800ml water,respectively.The drinking time and volume of water and walking after drinking water were similar to those in control group. Results The intestinal cleanliness was better and the adverse reactions were less in convention group 3 than in convention group 2 and control group（P＜0.05）. Conclusion Drinking 800ml water after taking 70ml magnesium sulfate can shorten the intestinal preparation time and reduce the adverse reactions.