Based on the rotating-compensator ellipsometry (RCE), a method of phase retardation measurement of wave plates based on the self-calibration method is presented. The new method takes retardation of compensator as an unknown parameter, constructs four nonlinear equations, and calculates the retardation of wave plates under test. The method uses the self-calibration of compensator to eliminate the systematic error caused by its retardation′s inaccurate calibration. Especially, it is more convenient for retardation measurement in many wavelengths. Based on this, the measuring accuracy of system is analyzed and simulated. It is found that the maximal systematic error and random error are 0.036° and 0.04°, respectively, over all the samples. Besides, a quarter wave plate (QWP), a half wave plate (HWP), a 127° wave plate and the air (without sample) are measured at 517.3, 525.0 and 532.4 nm, respectively, to evaluate the performance of the system, where the retardation of air indicates the measuring accuracy of the system, and is consistent with error analysis.