Taking the disk under diametral compression as an example, the whole-field isoclinic-angle phase of the model was analyzed according to elastic mechanics, and the principal-stress direction was put forward. Base on six-step phase shifting technique, the actual phase of whole-field isoclinic angle and whole-field isochromatic of a disk was extracted. Combining finite element software MARC with fitting of shape function, six-step phase shifting and isochromatic phase patterns of a ring under diametral compression were simulated. This method can be generalized to simulate the photoelastic experiment of stress model with complex analytic solution or without analytic solution. The feasibility of this method was proved by the experiments of a disk under diametral compression, and the information of whole-field isochromatic could be extracted automatically.