Abstract: The chemical reaction characterization and rheological property of KH-370 polyimide resin were characterized by DSC, TG, FTIR and rheometer. The QWB200/KH-370 composite was prepared by hot pressing technology with QWB200 quartz fiber as reinforcement.The effects of different process parameters (pressing temperature, pressure, curing temperature) on the mechanical properties of QWB200/KH-370 composites were studied. On this basis, the molding process system of the composites was determined.The mechanical strength of the composite at 400℃ and the dielectric properties at broad frequency were also investigated. According to the results, the best process parameters for the preparation of QWB200/KH-370 composites are: pressing temperature of 290-310℃, pressure range of 3.0-4.0 MPa, curing temperature of 380℃. The prepared QWB200/KH-370 composites exhibit excellent mechanical properties at room temperature, and the retention rates of mechanical strength at 400℃ is above 58%, showing good heat resistance. The QWB200/KH-370 composites show stable dielectric constant and dielectric loss at broad frequency from 1 GHz to 18 GHz.