Numerical simulation method is widely used in studying ice-storage process in an ice-storage system. In this paper, the three-dimensional dynamical mathematical model of the ice-storage process in a single tube is established and the process is solved by the enthalpy method. Effects on the performance of heat-exchange, caused by variation of velocity of the refrigerant, inner diameter of the tube, initial temperature of the external water and inlet temperature of the refrigerant, are simulated and analyzed.