Numerical simulation was applied to calculate temperature changes of injection molded HDPE in the cooling process．Based on the cooling model of low molecular crystalline material

the governing equations were developed to describe the cooling temperature of solid

liquid

and solid-liquid interface

respectively．An enthalpy E and a parameter T* were employed to convert the energy equation into a non-linear equation

which was then disereted by the control volume finite difference approach and solved with mathematical software Matlab．The calculated temperature profile exhibited the existence of thermosphere and phase transformation and required a time period of 2 min for the cooling cycle

which Was in agreement with the experimental data for the inner layer of the HDPE sample．Thus it can be applied to the numerical performance of Stefan problems．The effect of molding conditions on the cooling temperature of HDPE was also discussed

which can reflect the change of its crystalline hehavior.