This paper is intended to improve efficiency of two-phase BLDC motor using analytical and statistical methods, and then the stability of the starting for the designed model is investigated. The characteristics of the motor according to magnetization directions of permanent magnet are analyzed through the analytical method, and design variables that affect the efficiency are selected. Preliminary optimal design is performed using the analytical method with the design variable. The RSM (Response Surface Method) based on the FEA (Finite Element Analysis) is applied to complement errors of the analytical method. As a result, the optimal design is determined. Finally, the stability of the starting for the optimal designed model is evaluated by analyzing cogging torque, and it is verified through the FEA.