In order to realize a liquid crystal variable retarder (LCVR) to precisely control the phase delay for different wavelengths of the incident light and expand its application advantages in the field of optical information and optical measurements, its birefringence dispersion characteristics are studied and analyzed. Firstly, according to the index ellipsoid theory, LCVR birefringence dispersion of the incident light is matched with Cauchy dispersion; Secondly, retardance for 532, 635, 670 nm laser is measured, which changes with the value of drive voltage; Finally, the above three measurements are analyzed, the coefficients about empirical formula of Cauchy dispersion are solved, and a calibration method of dispersion used a normalizing way is established and verified with a 650 nm laser. Experimental results show that LCVR produces birefringence dispersion for different wavelength incident light. For 650 nm laser, the retardance deviation between experimental result and dispersion calibration is given not more than 0.007λ , which proves the calibration method is accurate and feasible.