The evaluation method for a biaxially oriented film using in-situ measurement during the stretching process was developed. It can obtain basic data such as stress-strain curve, birefringence, light scattering, three-dimensional refractive indexes and birefringence distribution. Stress and strain as functions of time, temperature and percentage in elongation, the information of superstructure on the deformation in molecular of polymer can be obtained by measuring the birefringence and light scattering during the biaxial stretching process with a small amount of sample. The results of experiments show that the stress, retardation and three dimensional molecular orientation behavior during the simultaneous biaxial stretching and sequential biaxial stretching process. Stretchability, thickness uniformity and spherulite size can be obtained a‚” the same time. Key words: stretching process, in-situ measuring, birefringence, light scattering, three-dimensional refractive indexes