The present invention provides a thermal management system, an X-ray detection device and a CT apparatus. The thermal management system comprises a heater, an air mixing portion and a fan. The heater is provided at an air inlet of the air mixing portion. The air mixing portion provides an air mixing space for mixing exterior air that enters the air mixing portion with interior air of the air mixing portion. The fan is provided at an air outlet of the air mixing portion, and supplies the mixed air in the air mixing portion to a target object to be thermally managed. Therefore, a response time of the thermal management system to operate for an external temperature change may be lengthened, thus occurrence of abrupt change in a temperature of the target object as the external temperature changes abruptly may be avoided, improving a reliability of the thermal management system.
