This work throws light to study the changes of optical birefringence for cold drawn high density polyethylene (HDPE) thin film at different stresses. A stress-strain device connected to a scattering optical system was used to investigate the dynamical behavior of opto-mechanical properties at room temperature (27 degrees C +/- 1 degrees C). Some structural parameters, optical and mechanical orientation factors, f(theta), f(2)(theta), f(4)(theta), f(6)(theta), F(av), P(2)(theta), P(4)(theta), f(c), and f(m), were calculated. Also, the distribution segments at an angle (theta), the number of random links per chain (N(1)), the number of chains per unit volume (N(c)), and the average work per chain W' were calculated. The average value of the maximum birefringence was evaluated. The obtained studies demonstrate changes to the molecular orientation functions and evaluated micro structural parameters as a result of the applied cold-drawing process on (HDPE) thin film. Relationships between the calculated parameters and draw ratios were presented for illustration. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 2026-2032, 2011