Objective To explore the effect of free anterolateral thigh flap transplantation combined with closed negative pressure drainage on flap repair effect in patients with tibial fracture complicated by soft tissue defect. Methods A total of 50 patients with tibial fracture complicated by soft tissue defect admitted to the 942nd Hospital of the Joint Logistics Support Force of the Chinese People's Liberation Army from January 2020 to January 2025 were selected, and they were divided into the control group and the observation group by the random number table method, with 25 patients in each group. The control group was treated with free anterolateral thigh flap transplantation, and the observation group was treated with free anterolateral thigh flap transplantation combined with closed negative pressure drainage. The number of dressing changes, wound healing time, flap repair effect, complication rate and ankle joint function were compared between the two groups. Results The number of dressing changes in the observation group was fewer than that in the control group, and the wound healing time was shorter than that in the control group (P <0.05). The excellent and good rate of flap repair in the observation group (96.00%) was higher than that in the control group (72.00%) (P <0.05). The incidence of complications in the observation group (4.00%) was lower than that in the control group (28.00%) (P <0.05). The ankle joint function of the observation group at 3 months after surgery was better than that of the control group (P <0.05). Conclusion The application of free anterolateral thigh flap transplantation combined with closed negative pressure drainage in the treatment of tibial fracture complicated by soft tissue defect can effectively reduce the number of dressing changes, shorten the wound healing time, improve the flap repair effect, reduce the incidence of complications, and promote the recovery of ankle joint function.