Abstract: To evaluate the thermal emission modes in manned spacecraft, the effectiveness and system cost of using three thermal emission modes of water sublimator, radiator, and both radiator and heat pump were compared and analyzed in three environments involving deep cold space, early morning near the equator of the moon, and midday near the equator of the moon. The following conclusions are obtained: the thermal emission mode of water sublimator is weight-saving in short-term missions; thermal emission capacity of the radiator can be improved significantly by using heat pump, and the improvement effect increases with the solar zenith angle; using heat pump costs greater energy consumption. Therefore, the selection of thermal emission mode requires a comprehensive evaluation according to mission scale, duty cycle, and power supply capacity of spacecraft.