Hallux valgus (HV) is a foot deformity that can be treated with Chevron osteotomy, and a modified plantarward oblique osteotomy has been proposed in recent years. However, no research has focused on the correctional power of the osteotomy. The aim of this study was to examine the character of this plantarward oblique Chevron osteotomy (POCO) and to determine the rationale of this method.Radiographs and clinical data from 65 HV patients (77 feet) with painful callosities were evaluated. The intermetatarsal angle, hallux valgus angle, and relative height of the second metatarsal were measured, and a valid width of the first metatarsal was proposed. A visual analogue scale (VAS) and the American Orthopaedic Foot and Ankle Society hallux-metatarsophalangeal interphalangeal scale (AOFAS) were used to evaluate the patients' clinical results.There were significant differences in the HVA and IMA. The decline in the height of the second metatarsal was positively related to the decline in the height of the first metatarsal, but the changes were smaller for the first metatarsal. Painful callosities disappeared in 77 feet, 4 (5.1%) patients had no pain but a remaining plantar callosity, and 2 (2.6%) patient had relieved pain with a plantar callosity after follow-up. The VAS scores improved from 8.58 ± 0.50 to 1.96 ± 0.75 points after the operation (p < 0.001). Significant differences were demonstrated in the AOFAS scores (65.81 ± 4.05 vs 87.88 ± 3.41, p < 0.001). The modified POCO prevents the dorsal migration of the metatarsal head, preserves other lesser metatarsals and provides an opportunity for patients who may possibly need additional future deformity correction. Therefore, POCO is a safe and effective method to treat hallux valgus and offers the superior potential benefits of correction and transfer metatarsalgia.