Diamond-silicon carbide (SiC) composite stacks are composed of two kinds of wide-bandgap materials, each of which has excellent thermal, electronic, optical, and mechanical properties, and is considered an ideal material for heat dissipation. For optimal application, the interface between the two materials needs to be almost void-free and of high-quality growth. Traditional methods such as sintering and liquid/vapor phase infiltration have many problems, but the preparation of diamond-SiC composites by the microwave plasma chemical vapor deposition (MPCVD) method can effectively solve these problems, overcome the interface defects, and break through the size limitation. In this review, various techniques for preparing diamond-SiC composites by MPCVD will be discussed. It mainly includes the co-deposition of diamond and cubic polytype β-SiC, deposition of diamond films on β-SiC/Si substrates, and deposition of diamond films on 4H-SiC and 6H-SiC substrates. The implementation methods, research progress, and application trend of each approach are reviewed in detail.