Active temperature control is adapted as an important mean for the spaceborne instruments to fit the harsh thermal environment. The way of active heating is used for the spaceborne instrument to control the temperature of its temperature sensitive component. The reliability of the temperature control module is directly related to the effects of the active temperature control measures, which may affect the instrument performance. Based on the temperature control circuit, the reliability comparison between two redundant design schemes is carried out, namely the system backup and the unit backup. The results showed that the backup system has higher reliability. According to the results of the reliability prediction, in combination with the on-board temperature control function module’s feature, the temperature control module was selected.