Since common peroneal nerve is easy be injured because of superficial position of caput fibulae, less surrounding soft tissue and poor mobility, injury of common peroneal nerve is a problem worth discussing in the field of trauma orthopedics. Common peroneal nerve injury often causes foot prolapse, inability in dorsiflexion and eversion, sensory disturbance of anterolateral side of the lower leg and dorsum of foot. In this article, a case of old injury of lateral collateral ligament of knee joint combined with an avulsion fracture of fibular head resulting in injury of common peroneal nerve was reported and repaired by surgery with good effects.