The invention discloses a heat sink simulator for nano-satellite space, which comprises an analogue unit, a data acquisition unit, a controller, a power driving unit and a communication unit. The analogue unit comprises a thermoelectric refrigeration sheet TEC, a heat flow sensor, a fan, a temperature sensor A, a temperature sensor B and fins; and the controller generates control signals of the TEC according to a feedback heat flow value acquired by the data acquisition unit and a given heat flow value as input of an algorithm controller, achieves good tracking of given heat flow by the feedback heat flow, namely, achieves good simulation of spatial radiation heat flow by heat conduction flow, transfers the heat led out by the TEC to the fins at the same time of ensuring heat flow tracking, achieves control of temperature of the fins by the fan according to control demand, radiates redundant heat to the air, and achieves simulation of spatial low temperature and black background environment. The heat sink simulator has the advantages of little thermal inertia, quick response speed and small volume, and achieves desktop representation of a nano-satellite heat test device.