Objective To analyze optimal amount of drinking water,ways of drinking water,timelimit of drinking water on the effect of bowel preparation for intravenous pyelography (IVP) examination after oral administration of 50% magnesium sulfate 60 ml. Methods 200 patients who gave their consentfrom June 2009 to February 2010 drank 50% magnesium sulfate 60 ml for IVP check were divided into four groups. Group A: a large amount of graded oral administration of warm water 1200 ml within 1h; Group B: a small amount of oral administration of warm water 1200 ml within 1h;Group C: a large amount of graded oral administration of warm water 2000 ml within 1h; Group D: a medium amount of graded oral administration of warm water 1200 ml within 2 h. And then the bowel preparation effect of the four gro ups were analyzed. Results Through the comparison, group A was much better than the other groups on the aspects of cathartic satisfaction, the effective degree of reading films and flatulence. Conclusions To take a large amount of graded oral administration of warm water 1200 ml within 1h can improve cathartic satisfaction,the effective degree of reading films and flatulence.