PET is a commercially important engineering thermoplastic with good thermal and mechanical properties, low permeability, and chemical resistance. It is used for food packaging. Biodegradable plastic PLA is derived from renewable resource. PLA is biodegradable polyester with high strength and high modulus by various applications in food packing. PLA products have been produced and start to challenge PET products. PLA is not a good barrier for oxygen and has relatively high cost. Blending is usually used to improve the properties of polymers. Many binary blends of the type A/B with A being either PET or PLA have been produced. The miscibility and thermal properties of PET/PLA Blends will study over a wide composition range from0% to 100% PLA. In this blend system, both PET, and PLA, have the potential to crystallize. We report the non-isothermal crystallization of a component, PET, with and without the presence of PLA crystals, and a component, PLA, with and without the presence of PET crystals. One polymer could affect the subsequent crystallization and crystallinity of its blend partner. Like the crystals, the rigid amorphous fraction of one polymer component may inhibit the growth of crystals of the other blend partner. Keywords: PLA, PET, Blend, Crystallization, properties