Objective To evaluate the effects of modified thoracolumbar interfascial plane block (M‑TLIP) on postoperative analgesia in children with lower limb dysfunction undergoing selective dorsal rhizotomy (SDR). Methods Sixty‑five children were selected for spinal nerve root dissection under general anesthesia. The children were divided into incisional infiltration group (group A, n=32) and modified thoracolumbar interfascial plane block group (group B, n=33) according to the random number table method. Group A received an incisional infiltration of 0.375% ropivacaine 0.5 ml/kg administered by the surgeon; in group B, an ultrasound‑guided modified thoracolumbar interfascial plane block was performed by the anesthesiologist after completion of anesthesia with an injection of 0.375% ropivacaine 0.5 ml/kg before the start of surgery, the electronic venous automatic analgesic pump was connected. The doctor recorded the general information (gender, age, weight), operation time, intraoperative doses of sufentanil and remifentanil, the postoperative Face, Legs, Activity, Cry, and Controllability (FLACC) scores at 1, 6, 12, 24, 36 h and 48 h, the number of postoperative analgesic pump compressions, the dose of sufentanil used for compression, the dose and the numbers of oral ibuprofen suspensions. Generalized estimating equations (GEE) was used to analyze the effects of different time and different analgesia on FLACC score of SDR children. Results There was no statistically significant difference in sex ratio, age, weight, duration of surgery, intraoperative sufentanil and remifentanil use between the two groups of children (all P>0.05); in group A, the FLACC scores at 1, 6, 12, 24, 36 h, and 48 h after surgery were higher than those in group B (all P<0.05), and the FLACC scores in group B were all≤3 points. The number of postoperative analgesic pump presses and the dose of sufentanil used to press were higher in group A compared with group B, the difference was statistically significant (all P<0.05). The number of postoperative oral ibuprofen suspensions and the dose were higher in group A than in group B, the difference was statistically significant (all P<0.05). GEE model analysis showed that different times and different analgesia methods had statistically significant effects on FLACC scores (all P<0.05). Conclusions The M‑TLIP for children with SDR provides better postoperative analgesia while reducing the dose of postoperative analgesics used in the children.