Objective To observe the effect of selective sacral rhizotomy in treating spastic bladder after spinal cord injury and to explore the mechanism and the best surgical method of different sacral rhizotomies. Methods The spastic bladder models were established in 12 male dogsand were divided into 4 groups according to the different rhizotomies of the sacral nerve as the following: rhizotomy of the anterior root of S2(group A), rhizotomy of the anterior root of S2 and half of the anterior root of S3(group B), rhizotomy of the anterior roots of S2 and S3(group C), and total rhizotomy of the nerve roots of S2-4 (group D). By urodynamic examination and electrophysiological -observation, the changes of all functional data were recorded and comparedbetween pre-rhizotomy and post-rhizotomy to testify the best surgical method. In clinical trial, according to the results of the above experiments, rhizotomy of the anterior root of S2 or one of the halfanterior root of S3 were conducted on 32 patients with spastic bladder after spinal cord injury. The mean bladder capacity, the mean urine evacuation and the mean urethra pressure were (120±30), (100±30)ml and (120±20) cm H2 O, respectively before rhizotomy. Results After rhizotomy, the bladder capacity in 4 groups amounted to (150±50), (180±50), (230±50), and (400±50) ml, respectively; and the urine evacuation volume were (130±30), (180±50), (100±50) and (50±30)ml, respectively. In the treated 32 patients, the mean bladder capacity were raised to 410 ml, and the mean urine evacuation volume were also increased to 350 ml. Incontinence of urine disappeared in all patients. After 22-month follow-up on 13 patients, no recurrence was observed. Conclusion The effectof selective sacral rhizotomy in treating spastic cord injury is significant and worthy of further studies.