Although water is one of the main components of cementitious materials, basic questions persist regarding its distribution and content in the hardened paste with complex internal pore network.In this article, the low field NMR, as a nondestructure and noninvasive technique, was employed to investigate the water distribution and content in cement paste with different water to cement ratio during early and later hydration stages.From the water distribution spectrum deduced from relaxation time distribution in paste, it suggested that the water was filling in the capillary pores at initial period, and then diffused to the mesopores and gel pores in hydration products as the hydration proceeding.The decrease of peak area in water distribution spectrum reflected the transformation from physically bound water to chemically bound water.In addition, based on the connection between relaxation time and pore size, the relative content changes of water in various states and constrained in different types of pores, were also measured.The results demonstrated that it was influenced by the formation of pore system and theoriginal water to cement ratio in the paste.