Objective:To explore the effects of lower concentrations of ropivacaine on ultrasound-guided nerve block in pediatric orthopedic surgery.Methods:Using a retrospective study method, 75 children who underwent orthopedic surgery at Wu Jiang District Children′s Hospital from May 2023 to February 2024 were selected and divided into Group A (25 cases, 0.15% ropivacaine nerve block), Group B (25 cases, 0.20% ropivacaine nerve block) and Group C (25 cases, 0.25% ropivacaine nerve block). The heart rate; mean arterial pressure; onset time of anesthesia; analgesic maintenance time; recovery time of movement and sensation; child face, legs, activity, cry, consolability behavioral tool (FLACC) score at 2 h after surgery; adverse reactions incidence of postoperative local anesthetic drugs were compared.Results:There was no statistically significant difference in the physical indicators of heart rate and mean arterial pressure among the three groups ( P>0.05). As the concentration of ropivacaine increased, the onset time of anesthesia in the three groups of children was shortened: (11.04 ± 1.02) vs. (10.44 ± 1.04) and (7.16 ± 0.85) min, and the differences between the three groups were statistically significant ( P<0.05); There was no statistically significant difference in the analgesic maintenance time among the three groups ( P>0.05). As the concentration of ropivacaine increased, the recovery time of movement and sensation was increased: (194.64 ± 20.43) min vs. (207.72 ± 22.34) and (250.32 ± 30.18) min, (176.44 ± 16.18) min vs. (189.24 ± 20.66) and (224.08±29.56) min, and the differences among the three groups were statistically significant ( P<0.05). There was no statistically significant difference in FLACC scores among the three groups of patients at 2 h after surgery ( P>0.05). The total incidence of adverse reactions in Group A was lower than that in Groups B and C: 4% (1/25) vs. 24% (6/25) and 52% (13/25), and the differences among the three groups were statistically significant ( P<0.05). Conclusions:The 0.15% ropivacaine used for ultrasound-guided nerve block in pediatric orthopedic surgery can achieve good anesthesia effects with low incidence of adverse reactions, and is worthy of clinical promotion.