Objective To investigate the effectiveness of Flow-through bridge anterolateral thigh flap transplantation in the treatment of complex calf soft tissue defects. Methods The clinical data of the patients with complicated calf soft tissue defects, who were treated with Flow-through bridge anterolateral thigh flap (study group, 23 cases) or bridge anterolateral thigh flap (control group, 23 cases) between January 2008 and January 2022, were retrospectively analyzed. All complex calf soft tissue defects in the two groups were caused by trauma or osteomyelitis, and there was only one major blood vessel in the calf or no blood vessel anastomosed with the grafted skin flap. There was no significant difference between the two groups in general data such as gender, age, etiology, size of leg soft tissue defect, and time from injury to operation (P>0.05). The lower extremity functional scale (LEFS) was used to evaluate the sufferred lower extremity function of the both groups after operation, and the peripheral blood circulation score of the healthy side was evaluated according to the Chinese Medical Association Hand Surgery Society’s functional evaluation standard for replantation of amputated limbs. Weber’s quantitative method was used to detect static 2-point discrimination (S2PD) to evaluate peripheral sensation of the healthy side, and the popliteal artery flow velocity, toenail capillary filling time, foot temperature, toe blood oxygen saturation of the healthy side, and the incidence of complications were compared between the two groups. Results No vascular or nerve injury occurred during operation. All flaps survived, and 1 case of partial flap necrosis occurred in both groups, which healed after free skin grafting. All patients were followed up 6 months to 8 years, with a median time of 26 months. The function of the sufferred limb of the two groups recovered satisfactorily, the blood supply of the flap was good, the texture was soft, and the appearance was fair. The incision in the donor site healed well with a linear scar, and the color of the skin graft area was similar. Only a rectangular scar could be seen in the skin donor area where have a satisfactory appearance. The blood supply of the distal limb of the healthy limb was good, and there was no obvious abnormality in color and skin temperature, and the blood supply of the limb was normal during activity. The popliteal artery flow velocity in the study group was significantly faster than that in the control group at 1 month after the pedicle was cut, and the foot temperature, toe blood oxygen saturation, S2PD, toenail capillary filling time, and peripheral blood circulation score were significantly better than those in the control group (P<0.05). There were 8 cases of cold feet and 2 cases of numbness on the healthy side in the control group, while only 3 cases of cold feet occurred in the study group. The incidence of complications in the study group (13.04%) was significantly lower than that in the control group (43.47%) (χ2=3.860, P=0.049). There was no significant difference in LEFS score between the two groups at 6 months after operation (P>0.05). ConclusionFlow-through bridge anterolateral thigh flap can reduce postoperative complications of healthy feet and reduce the impact of surgery on blood supply and sensation of healthy feet. It is an effective method for repairing complex calf soft tissue defects.