In order to eliminate the negative effect of temperature to resistive pressure sensor of automobile, a calibration circuit is required based on ZMD chip or MAX1452. The traditional calibration way of ZMD is four-point calibration that has the defects such as inefficiencies and complexity. Thus, a simplified calibration way, named as three-point calibration, is provided which is able to simplify the calibration equipment in practical manufacturing. Considerably, the calibration efficiency is improved from about one hour into 5 minutes every time. After calibrated, the output of pressure sensor change only with pressure and the deviation value is from -0.48%FSO to +0.84%FSO,in the designing range ±2%FSO.