The effects of polarization degree, extinction ratio and bias angle error of polarizer on performance of comparative Optical Current Transformer (OCT), were analyzed in detail by employing polarization analysis tools. The theoretical analysis result shows the comparative OCT can eliminate the influence of nonideal polarization degree and extinction ratio because of the sensor’s dual-input and dual-output structure, while the bias angle error brings great damage to the performance of the comparative OCT. This disadvantage can be decreased by adjusting position between polarizer and analyzer exactly and increasing reference DC magnetic field or correcting software. The experiment of comparative OCT is carried out, and the test result shows that the change of error of the comparative OCT is only 0.7% in the range of 50℃ temperature, while the change of error of an ordinary OCT is more than 16% before comparative compensation. Moreover, the temperature characteristic of comparative OCT is much more excellent.