Abstract: A constant temperature working environment is required for the equipments mounted in the satellite on orbit. The external heat flux will affect greatly the temperature of the equipments with small heat capacity. The phase change material (PCM) container is used in the thermal control design based on traditional methods. The governing equations for equipments, honeycomb panel and PCM container are derived by using enthalpy method and the heat transfer characteristics of PCM container in space are studied. The results show that the isothermal properties are improved and the temperature fluctuation is reduced by using PCM container. This research could provide a basis for the thermal control design of equipments mounted in spacecraft.