Abstract: The diamond films were synthesized on silicon substrate by hot filament chemical vapor deposition (HFCVD). The quality and electronic properties of the films were characterized by scanning electron microscopy(SEM), Raman spectrum, Cathodoleminesecence(CL) and the Hall effect measurements. The experimental results show that the deposition conditions have an important influence on the quality and electronic properties of diamond films. The carrier mobility decreases with increasing methane concentration. However, the field emission effect is enhanced with the methane concentration. The piezoresistive effect is degraded with increasing micro-defects.The gauge factor for the heteroepitaxial p-type diamond films is found to be 1200 at 100 microstrain for room temperature, but lower than 200 for poly-crystalline diamond films with a lot of defects. This is ascribed to the increase of defect state density and also dependes on the structure changes in the films.