The program of treatment and rehabilitation of chronic ankle instability is different according to the impairment degree of lateral ligament of the ankle. The diagnosis methods of lateral ligament's injury are magnetic resonance imaging (MRI) and arthroscopy, which are either invasive or time-consuming. This study aims to analyze the mapping relation between lateral ligaments' injury and center of pressure (COP) position shift via finite element analysis in order to explore a method that can diagnose lateral ligaments' injury. Two typical finite element method (FEM) bone models of heel-strike and toes-off phase are built according to the gait metrics. The lateral ligament is simulated by adding the spring to the model in the anatomical position and the injury of lateral ligament is simulated by reducing the stiffness of the spring. The contact pressure between the foot and support plate and COP coordinates are analyzed. The displacement of anterolateral shift of COP coordinates is mapped to the injury degree of lateral ligament. This study provides feasibility to diagnose lateral ligament injury by plantar pressure distribution.