Objective To evaluate the efficacy and safety of nusinersen in children with spinal muscular atrophy (SMA) types 2 and 3. Methods Prospective data were collected on motor function, compound muscle action potential (CMAP), and spinal Cobb angle from 29 children with SMA type 2 or 3 treated with nusinersen at the Children's Medical Center of Xiangya Hospital, Central South University, from January 2022 to November 2025. Pre- and post-treatment changes were analyzed. Results Of the 29 children, 19 (66%) had a follow-up duration of ≥26 months. Compared with baseline, after 26 months of treatment, clinically meaningful improvement was observed in 53% (10/19) on the Hammersmith Functional Motor Scale-Expanded (HFMSE), 78% (14/18) on the Revised Upper Limb Module (RULM), and 89% (16/18) on the Motor Function Measure 20-item/32-item (MFM-20/32). CMAP amplitudes increased from baseline in the bilateral median, ulnar, and radial nerves (P<0.05). The Cobb angle increased by a median of 6.2 degrees at 26 months of treatment (P<0.05). Compared with the non-rehabilitation group, the rehabilitation group showed greater improvement in MFM-20/32 scores and slower scoliosis progression (P<0.05). Across the 29 children, 309 intrathecal injections were performed; the incidence of procedure-related adverse reactions was 15.2% (47/309), and no serious adverse events were reported. Conclusions Nusinersen is well tolerated and safe in children with SMA types 2 and 3. The proportions achieving clinically meaningful responses on motor-function scales and CMAP improvements increase over time, and rehabilitation training may enhance efficacy.