A model for the heat transfer of  vacuum insulation panel（VIP）and polyurethane foam（PU）multiple-insulator applied to freezer is established and the relationship between the heat flux and thickness of VIP under different total thickness of the multiple-insulator is analyzed.Five curves of heat flux versus thickness of VIP corresponding to five kinds of total thickness of multiple-insulator are presented through simulation.The energy-saving effect and economic benefits from the VIP+PU multiple-insulator applying to freezer are further analyzed and then the optimal thicknesses of VIP in multiple-insulator and its corresponding invest recall-period under different total thicknesses are obtained.It is revealed that all the optimal thicknesses of VIP nearly have the same value of 0.01 m.The shortest invest recall period for the application of the multiple-insulator instead of pure PU insulator to freezer is 3.7 years.