A novel way using a polarized optical microscopy and statistical image analysis techniques for direct investigation of the crystallization kinetics and spherulitic morphology of poly (lactic) acid induced by casting film process has been proposed. DSC analyses were carried out to explore the effect of drawing in thermal properties of PLA. We found that the rate of cold crystallization was sharply increased with draw ratio. Isothermal calorimetric results reveal that thin films crystallize slowly compared to sheets. Moreover, thin films don’t fit the Avrami model demonstrating that more stretching may modify the crystallization kinetics of films. POM experiments showed the existence of two different spherulitic populations in thin films and two nucleation mechanisms was identified. Accordingly, the growth rate was found to be not linear with time. Furthermore, the X-Ray diffraction analyses showed the presence of α and α’ crystal form in thin films contrarily to sheets with α form. Afterwards, poly (ethylene glycol) was used to improve process ability, flexibility and ductility of PLA casting films. Rheological analysis showed an improvement of viscoelestic properties of PLA films and a decrease of thermal degradation in the extruder with addition of different amount of PEG. The presence of PEG as plasticizer was found to reduce major extrusion defects even at high shearing rate and improve the PLA casting films process. In addition, POM experiments revealed that the presence of PEG greatly controls the crystalline morphology of PLA. Obviously, PEG addition led to the development of finite spherulites nucleating close together which influences greatly the germination rate and the growth rate; but preserves the same nucleation mechanism of PLA. Finally, we have shown that the addition of PEG and optimized processing conditions lead to the development of new materials with controlled structures and good mechanical properties.