ObjectiveTo observe and assess the therapeutic effect of posterior amputation of internal sphincter and partial external sphincter in the treatment of old anal fissure. MethodsEighty patients with old anal fissure treated between August 2012 and June 2014 were randomly divided into study group and control group with 40 in each. The study group received posterior amputation of internal sphincter and partial external sphincter, while the control group underwent single amputation of internal sphincter. Then we observed the cure rate, wound healing days, pain at defecation after operation, defecation control after operation, and long-term recurrence rate. ResultsAll the 40 patients in study group were healed with a recovery rate of 100%, while 38 in control group were healed with a recovery rate of 95%; the difference between the two groups were not significant (P>0.05). The wound healing time in study group[(17.0±3.5) days] was much longer than that in the control group[(10.5±3.8) days] (P<0.05). The pain extents of fundament during defecating on the first day and 3, 7, and 15 days later in study group were more alleviated than those in the control group (P<0.05). In the six-month follow-up period, one patient in study group had liquid stools out of control 3 months after the surgery, and the others had no similar symptoms (P>0.05). ConclusionPosterior amputation of internal sphincter and partial external sphincter is a reasonable method for the treatment of old anal fissure. It can not only cure old anal fissure but also alleviate pain at defecation after operation and facilitate defecation.