The invention discloses a fluid loop control device applicable to a nano-satellite thermal control system, which comprises a heat collecting module, a fluid loop driving module, a heat-electricity converting module, and a bypass flow control module. In the fluid loop control device, a micro-channel heat exchange technique combining with a heat-electricity converting technique is adopted so that the fluid loop of a nano-satellite heat control system forms forced convection heat exchange. In tthe fluid loop control device, an initiative heat control mode including major loop self-driving and bypass auxiliary control is adopted, wherein with the initiative heat control mode, the waste heat of the nano-satellite is converted into electric energy to drive the fluid loop to perform the forced convection heat exchange so as to achieve the closed loop control of the heat control system, reduce the electric energy consumption of the nano-satellite, and achieve the temperature control inside the nano-satellite. The fluid loop control device is that micro-channel heat exchangers are arranged on a satellite borne device of the prior nano-satellite and then two ends of each micro-channel heat exchanger are connected with a conduct respectively to form a forced convection fluid loop which can reuse the heat generated in the working process of the satellite borne device, thus the energy of the nano-satellite is saved, and a condition for the nano-satellite to work for a long period is provided.