Objective To evaluate the effect of L4-S1 selective posterior rhizotomy for spastic equinus secondary to cerebral palsy. Methods Fifteen patients with spastic equinus secondary to cerebral palsy were selected for this study. The dorsal roots of L4-S1 were exposed through a L4-S1 laminectomy. Three to five rootlets from each root were electrically stimulated with a concentric needle electrode. The muscle responses were observed visually and registered by electromyography. Those rootlets with a much lower threshold were divided. The spastic degree of plantar flexor was assessed according to Ashworth scale 1 week before and 6 months after the operation. Results Reduction of spasticity was observed in plantar flexors. All the patients presented functional improvement of motor abilities without any complications. Conclusion Selective posterior rhizotomy (SPR) from L4-S1 dorsal roots is an effective procedure for spastic equinus secondary to cerebral palsy, howerer, the indications should be controlled strictly.