Abstract: In cosmic space, the equivalent temperature of a cold black environment is about 3 K and the heat absorption rate is 1, which can be considered an ideal black body with no heat radiation or reflection. In the absence of solar radiation, cosmic space is a completely cold and black space, and all the thermal energy emitted by an object is completely absorbed, so it is also called a heat sink environment. The simulation of cold black environments in space is currently achieved mainly by passing liquid nitrogen or other cooling media through the heat sink with a highly absorbent black paint sprayed on the inner surface. The heat sinks can be used to simulate cold and dark environments in space environment experiments. In view of the problems of large flow resistance and easy gas blockage in the existing honeycomb plate heat sink, a stainless steel plate heat sink structure with straight tube is proposed. In order to verify its performance advantages, a detailed simulation study of the fluid distribution and temperature distribution of this structure is carried out in this paper. In addition, liquid nitrogen is selected as the working medium, and the influence laws of various conditions （such as heat flow density, flow velocity, single tube width and tube spacing）on the temperature, flow characteristics and total flow resistance within the system are further investigated. The results showed that compared with the honeycomb plate heat sink, the straight tube plate heat sink effectively solves the problem of flow disturbance, the flow field is smoother, and the flow resistance is decreased. For straight tube type plate heat sink, when considering the heat transfer effect and differential pressure situation, there exists an optimum value for the inlet flow rate, which should not be too large.Through this series of in-depth analyses, it aims to provide a theoretical basis for the optimal design to effectively solve the technical difficulties encountered in traditional design.