PDC bit drilling rate equation is one measuring criterion of PDC bit work efficiency. The reasonable PDC bit drilling rate equation could predict the penetration rate and provide guidance for field operation. This paper studied the influences of the parameters on PDC bit drilling rate, such as rock drillability, cutting teeth diameter, specific weight on bit and rotate speed, and regressed the relation equations between the above parameters and drilling rate for cement rock, white sandstone, yellow sandstone, red sandstone and granite based on the laboratory rock breaking experiments. The results showed that the regression equation between specific weight on bit and drilling rate is quadratic polynomial for the soft and intermediate hardness rock, such as cement rock, yellow sandstone and white sandstone. The regression equation is quartic polynomial, the regression equation between rotate speed and drilling rate is quadratic polynomial for the intermediate hardness rock, such as red sandstone. The field data verification results of Daqing Oilfield medium-deep well showed the fractional error in actual drilling speed and forecast drilling speed between 3.03% and 9.23% and the average error is 6.397%. This explained that the modified PDC bit drilling rate equation could describe the drilling law preferably.