Objective To study the impact of medicine retention time and the therapeutic effect to the chronic renal failure by retention enema with Chinese traditional Medicine at different hour.Methods Totals of 60 patients with chronic renal failure disease were randomly divided into observation group (n=30)and control group (n=30).The observation group adopted enema at 7:00-9:00, and the control group adopted enema at routine hour ( 19:00 -21:00 ) .Following items were observed and compared between two groups: subjective feeling, adverse reflection, defecating ratio before enema, the appetency of defecating after enema, medicine retention time after enema, the Scr before and after enema, the change of BUN and Ua.The observation period was 30 days ( one period of the treatment) .Results Compared with the control group, the adverse reflection, such as bellyache, abdominal distension, anus ache, downfallen pressure feeling at anus were significantly relieved in observation group (P<0.05).The times & severity of the appetency of defecating after enema in observation group was reduced apparently than that in control group (P<0.05).The average defecating ratio before enema in observation group was significantly improved (83.3%vs 20.0%;χ2 =79.452,P<0.01).The retention time in observation group was ( 324.12 ±129.47 ) min, and that in control group was ( 225.32 ± 104.21)min,and the difference was statistically significant (t=4.605,P<0.01).The blood BUN, Scr, Ua were down after enema in both groups, but the improvement in observation group was significantly better than that in the control group (P <0.05).Conclusions By practicing retention enema with Chinese traditional Medicine at 7:00-9:00, the medicine retention time in intestines can be extended, and the therapeutic effect to the chronic renal failure can be improved.