Non-isothermal crystallization process of polyoxymethylene (POM) from the melts was studied by two-dimensional correlation infrared spectroscopy. A hybrid structure of FCC (1135 cm(-1)) and ECC (904 cm(-1)) during the crystallization from the molten state was found. Non-isothermal kinetics of POM crystallization was also investigated using DSC curves. A newly perturbation-correlation moving-window two-dimensional (PCMW2D) technique was used to explore the complex crystallization process. We determined three processes in crystallization. The first is the initial stage of the crystal nucleus growing or the formation of certain local ordered structures in the melts. It can be inferred the formation of the crystal nucleus of FCC is earlier than that of the ECC. The second is the maximum crystallization temperature of POM. The last is the further improvements of crystals (especially in ECC) and the crystallization of the cyclic POM of low molecular weight. However, this process of FCC is slower than ECC. The temperature-dependent IR spectra at reheating were also analyzed using PCMW2D. (C) 2011 Elsevier Ltd. All rights reserved.