The preparation and performance optimization of concrete materials are the basis for the structural development and application of 3D printed building. The macroscopic mechanical properties and long-term durability of 3D printed concrete materials are directly related to the microstructure of interface. The formation mechanism of interlayer interface moisture state (water film) of 3D printed concrete was clarified, the evolution law of water film with time for different printing layer thickness strips was tested, the effects of time interval, printing layer height and environmental state on the pore characteristics of interlayer interface were studied by using CT scanning technology, and the interaction mechanism among interlayer interface moisture state, pore characteristics and binding performance was revealed. The results show that the interlayer interface porosity decreases with the increase of interlayer interface water mass per unit area, and the interlayer interface moisture quality is a more direct factor affecting interlayer interface state than the printing parameters. The interlayer interface moisture state and pore characteristics directly affect macroscopic mechanical properties of 3D printed concrete materials.