Microwave composite substrate is one of functional composite materials composing of polymer and inorganic fillers, which is used in microwave band circuits for signal transmission, electrical connections, and supporting components. Microwave composite substrate is a fundamental, common and key material in aerospace, electronic countermeasure, 5G/6G communication and other fields. In the past two decades, the domestic development of microwave composite substrate has made a great progress, but it is still a challenge. This review represented the properties of a microwave composite substrate and elaborated the factors influencing the properties and the functional mechanism. Also, the properties of different microwave composite substrates were discussed according to the category of polymer matrix. The domestic and international research studies on the microwave composite substrates in the past decade was further described. In addition, the development of domestic microwave composite substrate was also prospected to provide some references for improving its manufacture.