Objective: To make a contrastive analysis of effect of fracture reduction with positive medial cortical support on unstable pertrochanteric fractures treated with proximal femoral nail antirotation (PFNA). Methods: A total of 113 patients (43 men and 70 women) with AO/OTA 31A2 hip fractures treated with PFNA between January 2017 and January 2019 in Traumatic Orthopedics of the Third Hospital Affiliated to Anhui Medical University was retrospectively analysed. The patients were divided into a positive medial cortical support group (n=75), a neutral medial cortical support group (n=21) and a negative medial cortical support group (n=17) based on the relationship between the medial cortex of the head and neck and that of the femoral shaft on the postoperative X-ray film. Age, sex ratio, operation time, blood loss, tip-apex distance, postoperative radiographic femoral neck length loss and neck-shaft angle loss, hip Harris score and complications were compared between the three groups. Results: All patients were followed up for 8 to 14 months, with an average of 10.6 months. There were no statistical differences between the three groups in age, sex ratio, operation time, blood loss and tip-apex distance (P>0.05). According to the imageological examination and the postoperative X-ray film in 6-month follow-up, patients in positive medial cortical support reduction group had significantly less loss in neck length and neck-shaft angle than those in negative reduction group. The former group had higher hip Harris scores (P<0.05). Conclusion: Fracture reduction with positive medial cortical support can build more stable support between femoral head-neck fragment and femoral shaft, and effectively avoid the incidence of postoperative complications.