[Objective] To investigate the clinical outcomes of extracorporeal shock wave therapy (ESWT) for ARCO stage II non-trau- matic femoral head necrosis with different lesion areas. [Methods] A retrospective study was done on 69 patients (101 hips) who received ESWT for ARCO stage II non-traumatic femoral head necrosis from January 2017 to September 2018. The patients were divided into two groups according to the area of necrosis measured on MRI before treatment, including 35 patients (52 hips) in the ≤30% group and 34 pa- tients (49 hips) in the ＞30% group. The clinical and imaging data of the two groups were compared. [Results] There were no serious adverse reactions happened in anyone of them during the therapy. Patients in both groups were followed up for 12-24 months, with an average of (20.63±11.26) months. The VAS and Harris scores, as well as hip flexion-extension range of motion(ROM) and internal-external rotation ROM variated in curve manner in both groups over time. At 6 months after treatment, the ≤30% group proved significantly superior to the ＞ 30% group in terms of VAS and Harris scores and hip flexion-extension ROM (P＜0.05) , whereas there was no statistically significant dif- ference between the two groups in term of internal- external rotation ROM (P＞0.05). At 12 months after treatment, the ≤30% group was sig- nificantly superior to the ＞30% group in terms of VAS and Harris scores, as well as hip flexion-extension ROM and internal-external rota- tion ROM (P＜0.05) . However, the ≤30% group was only significantly better than the ＞30% group in VAS score (P＜0.05) , whereas the dif- ferences in Harris score, hip flexion-extension ROM and internal-external ROM between the two groups became not statistically significant at the latest follow up (P＞0.05) . Radiographically, the lesion area, the degree of femoral head collapse, and the Tonnis scales of hip degen- eration significantly worsened in both groups at the latest follow-up compared with before treatment (P＜0.05) . At the last follow-up, the le- sion area and femoral head collapse in the ≤30% group remained significantly smaller than that of the ＞30% group (P＜0.05) , but there was no significant difference in the extent of Tonnis degeneration grades between the two groups (P＞0.05) . [Conclusion] ESWT does consider-ably relieve pain and improve hip function within 12 months, especially for those with smaller lesion areas of ARCO stage II non-traumatic femoral head necrosis.