TC4 titanium alloy was formed by selective laser melting (SLM) process. The influence of laser power P and scanning speed V on the density and surface hardness of multilayer parts was studied by using two-factor controlled variable method from the aspect of input energy density. Experimental results show that when the energy density per unit volume of powder is 119.05 J/mm3<φ<166.67 J/mm3, the density of the molded parts can reach 96.62%～97.41%, and the surface microhardness can reach 415.2～425.4 HV, which is higher than the microhardness of powder particles before molding 335.4 HV. When the laser power is P=200 W, the scanning speed is V=600 mm/s, the powder thickness is H=0.04 mm, and the scanning distance is S=0.06 mm, the density of the formed parts reaches 97.41%, the surface microhardness reaches 440.5 HV, and the formed titanium alloy parts have good mechanical properties.