Ti150 powders were deposited on the as-forged Ti180 alloy by selective laser melting under different laser powers. The microstructure and mechanical properties of the Ti150/Ti180 bimetallic alloys were systematically studied. The results showed that the Ti150/Ti180 bimetallic alloy samples can be categorized into three regions: the forging zone, the bonding zone, and the deposition zone. The forging zone exhibited duplex microstructure. The bonding zone had no macroscopic defects. In the lower region, the Ti180 alloy underwent rapid melting and solidification, and formed a unique microstructure after undergoing multiple thermal cycles. In the upper region, there was a continuous variation in solute element concentrations, leading to the gradual transformation of the microstructure into Widmanstätten structure. The deposition zone consisted of Widmanstätten structure that was composed of α phase and residual β phase. As the laser power increased, the density in the deposition zone initially increased and then decreased. The main defect type shifted from lack-of-fusion to pores. The tensile properties showed a trend of initial improvement followed by deterioration. When the laser power was 287 W, the deposition zone has the lowest defect content, with a relative density of 99.58%. The ultimate tensile strength and elongation of the sample at room temperature were 1151 MPa and 4.8%, and those at 450 ℃ were 969 MPa and 14.0%, respectively.