Objective To explore the effectiveness of proximal femoral nail antirotation (PFNA) combined with mini plate for reconstruction of lateral femoral wall in the treatment of type AO/Orthopaedic Trauma Association (AO/OTA) type 31-A3 intertrochanteric fracture. Methods The clinical data of 70 elderly patients with AO/OTA type 31-A3 intertrochanteric fracture treated between January 2013 and January 2018 were retrospectively analyzed. They were divided into group A (PFNA alone, 35 cases) and group B (PFNA combined with mini plate reconstruction of lateral femoral wall, 35 cases). There was no significant difference in the general data of gender, age, side, cause of injury, time from injury to operation between the two groups (P>0.05). The operation time, intraoperative blood loss, fracture healing time, postoperative complications, and the tip apex distance (TAD) at 2 months after operation were recorded and compared between the two groups. Harris hip score was used to evaluate the function at 12 months after operation. Results Both groups were followed up 9-21 months, with an average of 16.6 months. The operation time and intraoperative blood loss in group A were significantly less than those in group B (P<0.05); there was no significant difference in TAD between the two groups at 2 months after operation (t=0.096, P=0.462). There were 5 complications (14.3%) occurred in group A, including 2 cases of blade perforating from the hip joint, 2 cases of screw back out, and 1 case of bone nonunion; only 1 case (2.9%) in group B had screw back out after operation; there was no significant difference in the incidence of complications between the two groups (χ2=2.917, P=0.088). All the fracture healed in group B, and 1 patient in group A suffered bone nonunion and eventually main nail fracture. The healing time of fracture in group A [(15.6±2.7) weeks] was significantly longer than that in group B [(12.5±2.5) weeks], showing significant difference (t=2.064, P=0.023). At 12 months after operation, according to Harris score, the results were excellent in 5 cases, good in 9 cases, fair in 13 cases, and poor in 8 cases in group A, the qualified rate (Harris score>70) was 77.14%; and the results were excellent in 7 cases, good in 11 cases, fair in 16 cases, and poor in 1 case in group B, the qualified rate was 97.14%; there was significant difference in the qualified rate between the two groups (χ2=6.248, P=0.012). Conclusion Compared with PFNA alone, the treatment of AO/OTA type 31-A3 intertrochanteric fracture with PFNA combined with mini plate reconstruction of lateral femoral wall can significantly reduce postoperative complications, promote fracture healing, and improve functional recovery of patients after operation.