Abstract: The combined radiation and conduction heat transfer in multilayer perforated insulation material MLPIM in orbit were investigated.The energy equation of the reflective screen was established.Combining the finite differential method the model for transient temperature calculation of the reflective screens in MLPIM and the model of inner radiation were presented.The space environment was looked as a screen in the whole model,which was convenient to deal with the boundary condition.Comparing the calculational result with the model to the calculational and experimental result in the reference at the analogical conditions it was proved that the model was feasible to apply in the engineering.The calculational result in another example shows the characteristics of the transient temperature and heat flux of the MLPIM in orbit and the characteristics of the temperature distribution of the reflective screens.This model provides the theoretical basis for the thermal performance study and optimum design of perforated multilayer insulation material.