The effect of hydroxyethyl methyl cellulose(HEMC) on the morphology of calcium hydroxide(Ca(OH)2) and the formation of polymer films in cement paste at different curing ages were studied by using environmental scanning electron microscopy(ESEM). The results show that HEMC dramatically affects the morphology and the oriented growth of Ca(OH)2 in cement paste. HEMC also increases the enrichment of Ca(OH)2 in pores, thus enhances the multidirectional growth of Ca(OH)2 which exhibit X shape or petal like morphologies both in cement paste and in pores, especially at earlier hydration time. Tiny linear polymer films of HEMC are formed in cement paste, bridging the Ca(OH)2 plates and even covering on them, and accordingly to improve the interfacial characteristics of Ca(OH)2 plates.