Abstract: Co-Si filler is used to join the Si BCN,the CTE of which is similar to each other. The joint is composed of Si + CoSi₂ eutectic structure. There is no obvious reaction layer,but the chemical bond is established between the solder and the ceramic base material. The method of adding active element Zr is tried to improve the wettability,but the appearance of Zr-Si compounds can significantly reduce the strength of the joint. Therefore,increasing the brazing temperature is a good way to improve the wettability. The shear strength of the joint is close to the strength of the base metal. The highest shear strength is 26 MPa.