An improved approach to determine the birefringence dispersion of a liquid crystal cell was presented. Using the local maxima or minima of the transmittance spectrum of liquid crystal cell is a very convenient method for this aim with the proviso that at least one birefringence value must be known in advance from which the interference orders corresponding to maxima or minima are determined. Presented approach overcomes this problem. The improved method was based on the minimizing procedure leading to the determination of interference order and Cauchy parameters accurately. It was tested on a theoretically generated transmittance spectrum of liquid crystal cell and the details of the fitting procedure were discussed.