The effect of mineral admixtures and chemical admixtures on the rheological behavior, setting time and printability of 3D printing mortar was studied. The results show that the addition of blast furnace slag and silica fume can significantly improve the rheological properties, prolong the operating time and printability of 3D printing mortar. With the increase amount of water reducing admixture, the viscosity, yield stress and thixotropy of 3D printing mortar are reduced, and the setting time is prolonged. However, too low dosage or too high dosage of the water reducing admixture will adversely affect the printability of 3D printing mortar. By adding appropriate retarder the viscosity and yield stress of 3D printing mortar can be reduced and its extrudability can be improved. With the increased dosage of gypsum, the apparent viscosity, yield stress, thixotropy and effective printing height of 3D printing mortar first decrease and later increase while the performance of extrudability shows the opposite.