The retardation error, the fast axis angle error of wave-plate and the angle error of polarizer are the main error sources of polarimeter based on rotating quarter-wave method. The measurement accuracy can be effectively improved by calibrating the polarimeter. A new simple calibration method of polarimeter is proposed. Horizontal linearly polarized light [1,1,0,0]T is used as a standard reference light, and it is measured when the polarizer is fixed on 0° and 45° respectively. The parameter errors of device can be calculated and obtained to calibrate the polarimeter. The experimental results show that the measurement error is reduced by the proposed method from 3% to less than 0.87%.