The miscibility and phase behavior of the blends of polyoxymethylene (POM)/Novolak were investigated by the cloud point method, which showed that the POM/Novolak blends exhibited a tower critical solution temperature. The melting point of POM decreased when diluted with Novolak. From the melting temperature depression of MOM, a negative interaction parameter (X) between POM and Novolak was obtained. The IR spectrum revealed that the miscibility between POM and Novolak was caused by the specific interaction between the OH groups of Novolak and the ether oxygen atoms of POM. The morphology of the blends investigated by polarized light microscopy showed that the size of spherulites of POM was sharply decreased by its mixing with Novolak. This suggests that Novolak be used as a compatibilizer for POM. The miscibility and phase behavior of the blends of polyoxymethylene (POM) / Novolak were investigated by the cloud point method, which showed that the POM / Novolak blends exhibited a tower critical solution temperature. The melting point of POM decreased when diluted with Novolak. From the melting temperature depression of MOM, a negative interaction parameter (X) between POM and Novolak was obtained. The IR spectrum revealed that the miscibility between POM and Novolak was caused by the specific interaction between the OH groups of Novolak and the ether oxygen atoms of POM. The morphology of the blends investigated by polarized light microscopy showed that the size of spherulites of POM was sharply decreased by its mixing with Novolak. This suggests that Novolak be used as a compatibilizer for POM.