In practical applications, the traditional Whitt passive point target calibration algorithm often leads to the problem of incorrect solution of polarimetric distortion matrix, which makes it impossible to calibrate the polarimetric distortion correctly. To solve this problem, on the basis of analyzing the cause of failure in solving the distortion matrix of the commonly used Whitt algorithm, a new polarimetric calibration method using 22.5° dihedral was proposed, including a new calibrator set, a preprocessing procedure for measured polarimetric scatter matrix and a new eigenvalue match rule, which could prevent wrong eigenvalue match result and thus wrong calibration result effectively. Simulation results verify its effectiveness and robustness.