OUFTI-1 is the first nanosatellite developed at the University of Liège and even the first one ever made in Belgium. This student project takes place within the framework of a long-term goal program called LEODIUM (Liège in Latin). The goal of this program is to provide hands-on experience to engineering students through the development of a series of nanosatellite for scientific experiments in cooperation with space industries of the region of Liège. OUFTI-1 will be the first satellite ever equipped with one of the latest digital amateur radio communication protocol : the D-STAR protocol. This technology represents one of the three payload of OUFTI-1, since one target of the mission is to test this new protocol in space. The two other payloads are high efficiency solar cells provided by Azur Space and an innovative electrical power system developed with Thales Alenia Space ETCA. OUFTI-1 will hopefully be launched on the new European launcher Vega with eight other student nanosatellites. This present thesis focuses on the thermal design of OUFTI-1 whose goal is to guarantee all components are functioning within their allowable temperature range. With this in mind, different thermal model of increasing complexity are developed within both Matlab/Simulink and ESATAN/ESARAD environments. based on their results, proper measures will be taken to ensure all the components works indeed in their allowable range of temperatures.