Introduction Selective posterior rhizotomy (SPR) is a preferred procedure for relieving spastic children with cerebral palsy, but it is associated with severe pain and significant emergence agitation (EA). The thoracolumbar interfascial plane (TLIP) block provides an effective blockade to the dorsal branch of the spinal nerve. We hypothesise that the TLIP block may be an effective tool to alleviate EA and postoperative pain scores in children with cerebral palsy undergoing SPR. Methods and analysis This study is a single-centre, randomised, parallel-controlled trial being conducted in Beijing, China. A total of 50 paediatric patients with cerebral palsy scheduled for SPR are randomised in a 1:1 ratio to receive bilateral TLIP block with 0.2% ropivacaine 0.5 mL/kg or control. Patients in the TLIP group receive general anaesthesia combined with TLIP block, while patients in the control group receive only general anaesthesia, without a TLIP block. The primary outcome is the Paediatric Anaesthesia Emergence Delirium Score. The secondary outcomes are the incidence of EA, the Wong-Baker Faces Pain-rating Scale, the perioperative haemodynamics, the intraoperative remifentanil and propofol dosage, the extubation time and recovery time, and adverse reactions. Ethics and dissemination This study was approved by the Ethics Committee of Dongzhimen Hospital, Beijing University of Chinese Medicine on 21 September 2023 (2023DZMEC-379–02). Written informed consent is obtained from the legal guardian of each patient. The results of this study will be published in peer-reviewed international journals. Trial registration number ChiCTR2300076397