Semi-crystalline polymers are composed of crystalline lamellae and entangled amorphous chain in between. In molten state, the system is filled up with random coiled chains entangled by each other. When a polymer is not melted completely due to melted temperature, some traces of small crystallites or even part of crystallites entities are remained, which will influence the crystallization kinetics, crystallization peak temperature, or even polymorph modifications in the following crystallization process. To some extent, the crystallization behavior can display the characteristics of molten state. The subject of this work is to investigate the effect of initial polymorph on crystallization behavior under different melt temperatures for propylene-ethylene copolymer with ethylene counit of 4%. Pure α form and γ form used as initial state were prepared by adjusting crystallization temperatures in the beginning. The initial state was heated to Tmelt and kept at that temperature for 5 min. The change tendency for peak of crystallization recorded during cooling at rate of 10 K/min to 25 oC was different for two polymorphs. Tp of initial state of α form started to increase at higher Tmelt. Then WAXD measurements were done on the sample taken out from sample holder at room temperature and results were shown in figure 1. Two factors leading to the higher fraction of γ form for Tmelt from 160 oC to 120 oC include more nuclei remained in the system and strong epitaxy ability of γ form on α substrate of initial state of α form. Acknowledgements: This work is supported by NSFC (21134006) and ExxonMobil. We thank Dr. R. Wittenbrink at ExxonMobil Asia Pacific Research and Development Company, Ltd. for helpful discussions.