Abstract: 3D printing geopolymer is a new type of building way and material with both of resource utilization and intelligent building. The mechanical properties in all directions and the bonding strength between layers of components are important factors affecting the constructability and durability of buildings.3D printing geopolymer mortar was prepared with fly ash and quartz sand as main raw materials, anhydrous sodium silicate as alkali activator, slag powder as auxiliary cementitious material, magnesium aluminum silicate as special additive. The 3D printing component of fly ash-based geopolymer was prepared under the condition of the optimum dosage and proportion. The interlayer bonding strength and tensile strength were studied, and the mechanical anisotropy properties were characterized by mechanical properties and ultrasonic pulse velocity.