Abstract: In this paper, according to the density of the sintered ring products（2.15±0.05g/cm3,about 90%T.D.） as the design benchmark,the hot pressing process, and the microstructure and properties of boron carbide ring products for TOPAZⅡ space nuclear power plant use nuclear-class boron carbide as raw material were studied. The experimental results showed that the boron carbide ring products prepared by the hot pressing condition of 2 150 ℃ and 20MPa for one hour can meet the design density requirements. The abundance of ring products are more than 85%, the average grain size is less than 15 μm and the pore size is less than 5 μm.In the room temperature range to 620℃, with the increase of test temperature, the physical properties and mechanical properties showed different trends, linear expansion coefficient increases gradually, thermal conductivity reduces gradually and bending strength, and compression strength reduce gradually. All the measured data can be used as a reference whether boron carbide ring products can guarantee the structural integrity and performance stability under various operating conditions of TOPAZⅡ space nuclear power plant.