The invention relates to the technical field of aerospace thermal control, and discloses a thermal control device of a cold air propulsion module outside a satellite capsule. The cold air propulsion module is mounted on a satellite capsule deck through fasteners; the thermal control device comprises a positive temperature coefficient thermistor heater, heat insulation pads and a multi-layer heat insulation assembly, wherein the positive temperature coefficient thermistor heater covers the outer surface of the cold air propulsion module; the multi-layer heat insulation assembly is arranged on the outer sides of the positive temperature coefficient thermistor heater and the cold air propulsion module in a wrapping manner; and the heat insulation pads are mounted between the fasteners and thesatellite capsule deck and between the satellite capsule deck and the cold air propulsion module. According to the thermal control device disclosed by the invention, the positive temperature coefficient thermistor heater having adaptive temperature control capability is adopted for heating before the cold air propulsion module works, so that a thermal controller and a temperature sensor are not needed, the system is simple, the cost is reduced, and the reliability of the thermal control device is improved.