In evaluating the efficiency of heat pump system, the efficiency of the superheat control process plays an important role. In this study, the mathematical model of superheat control of electronic expansion valveevaporator system is developed, with the control strategy investigated. The model is identified by the least squares algorithm based on the minimized sum of squared residuals. The model consists of heat transfer relations concerning the fundamental equipment in the system such as thermal energy storage tank, electronic expansion valve, condenser, and evaporator. Different fuzzy control strategies, combined with optimal control algorithm, are investigated in detail to validate the deduced mathematical model of superheat control process.