Abstract: The measurement while drilling is an effective method to obtain the drilling parameters, one of the key techniques is to eliminate the temperature drift caused by the temperature change and installation error of the sensor. Based on the posture mathematics model and analysis of error sources of MWD inclinometer, we established the compensation mathematical model of temperature drift error and installation error on the basis of polynomial fitting of least square method and multi variable function for optimal solutions under constraints. The temperature error and installation error based on ADXL345 accelerometer were studied, the output of the inclination angle after compensation achieved high accuracy, satisfied the accuracy requirements of the measuring inclinometers, it shows that the error compensation mathematical model is correct, and can be applied to the error compensation of measurement while drilling inclinometer.