Abstract: Three-dimensional heterogeneous integration technology is the most important method to realize the development of electronic information systems towards miniaturization, high performance, high integration, low power consumption and low cost, and is also a core high-tech which determines the future development of microelectronics and micro-nano systems in the information platform. This paper introduces the advantages of 3D heterogeneous integration technology in the millimeter wave band, the development trend in recent years, and the challenges it faces. The fabrication process of our inhouse silicon-based MEMS photosensitive composite film is developed to provide very high-density integration and very low insertion loss of interconnections between chips. At the same time, three-dimensional integration of passive components such as high-performance packaged filters and high-radiation efficiency antenna-in-package can also be obtained. Finally, this paper introduces a novel millimeter-wave three-dimensional heterogeneous integrated radar and its application in long-distance vital sign detection.