The invention discloses a predicting method for pre-drilling pressure. The predicting method includes the steps that A1, sound wave speeds V at different depths of a target well area are obtained through seismic data, and corresponding formation pore pressure coefficients Cp predicted initially are calculated according to the speeds V; A2, the formation pore pressure coefficients Cp predicted initially are corrected to obtain formation pore pressure coefficients Cpj of the target well area. According to the predicting method for the pre-drilling pressure, correction is carried out based on the formation pore pressure coefficients, predicted initially, of the target well area, so that the corrected formation pore pressure coefficients of the target well area approach measured values, and the prediction accuracy is improved.