Over-pronated foot and over-supinated foot are the variations in foot posture from normal, recognised as risk factors for shin splints and knee pain, etc. Foot postures was conventionally assessed by the center of pressure excursion index (CPEI). However, the measurement systems are complicated and expensive. We aim to establish simpler methods for foot posture assessment using foot-motion measured by in-shoe motion sensor (IMS) system. We discovered seven and six effective predictors for CPEI estimation for male and female. The constructed CPEI estimation models by linear regression achieved RMSEs of 7.99 and 4.81 for male and female, and achieved “fair” agreement between estimated and true values.