To calibrate the phase retardance of a Liquid crystal variable retarder (LCVR) , its birefringence dispersion characteristic was analyzed, and the Support vector machines (SVM) algorithm was adopted to establish the prediction model. The obtained SVM decision function was used as a part of LCVR phase retardance, which was generated by the driving voltage. The experimental verification was carried out with a 568 nm laser. The results show that the deviation of the experimental value and the theoretical value is about 0.0061λ. SVM method could be used as an effective method for LCVR phase retardance characteristic calibration.