Si3N4 is an inorganic nonmetallic material with high hardness, high mechanical strength and high thermal stability. It is widely used in cutting tools, biomedicine, electronics, military and automobile fields. However, due to the hard and brittle characteristics of Si3N4 itself, surface defects are formed during processing, which greatly reduces the reliability of Si3N4 ceramics. A large number of studies show that the composite ceramics prepared with Si3N4 as matrix can effectively make up for the shortcomings of single Si3N4 ceramics. Among them, the composite ceramics prepared by adding BN as the second phase are particularly attractive in advanced engineering applications. BN ceramics exhibit good electrical insulation, oxidation resistance, and corrosion resistance. It has a good application prospect as a heat conductive and insulating material. In addition, the densification process and grain growth of composite ceramics are affected by sintering process, thus changing the properties of composite ceramics. Therefore, the excellent properties of the two materials are taken into account by adding BN to the Si3N4 ceramic matrix, the mechanical properties and dielectric properties of Si3N4-based composite ceramics are improved. In addition to thermal conductivity, Si3N4/BN composite ceramics also have other properties such as burning resistance, thermal shock resistance and microwave absorption. The mechanism research and structural design of sintering technology of Si3N4/BN composite ceramics need to match the current application requirements of ceramic materials, and the further improvement of its properties is still the focus of current research. In this review, the sintering process of Si3N4/BN composite ceramics is introduced, and the research progress of properties of Si3N4/BN composite ceramics in recent years is summarized. Finally, this study outlines the current challenges and areas for further research in Si3N4/BN composite ceramics development.