In order to determine the stress retardation distribution of optical glass, a novel method based on phase shifting algorithm and autocollimation method is proposed. An enlargement of the retardation of specimen can be achieved because of the autocollimation architecture. The phase shift step is fixed on according to the contrast of stress fringe patterns. The stress retardation can be acquired by analyzing a set of phase shifting stress fringe patterns with high contrast. The simulated result shows an accuracy of 0.2 nm/cm. The experimental result indicates that the retardation in the central area of annealed glass cube is 3 nm/cm while in the edge area it is 9 nm/cm. Fast stress retardation measurement with high precision can be realized by this method.