The Ti6Al4V and Inconel 718 dissimilar metals are welded using the continuous laser-induced eutectic reaction brazing technology. In this study, the influences of heat input on the microstructure and mechanical properties of the joints are systematically studied. The test results prove the formation of a large number of Ti_xNi_y intermetallic compounds in the fusion zone because of the excessive melting of the niobium interlayer at a heat input of 48 J/mm, resulting in the direct cracking of the joint. When the heat input is decreased to 40 J/mm, the unmelted Nb interlayer successfully inhabits the mixing of Ti6Al4V and Inconel 718 in the molten pool, preventing the formation of the Ti_xNi_y intermetallic compound in the joint. Further, two different metallurgical bonding interfaces, i.e., the (Ti, Nb) melting interface and the Nb/Inconel 718 eutectic reaction brazing interface, are obtained. Additionally, the (Ti, Nb) melting interface and the Nb/Inconel 718 bonding interface are separated by the unmelted Nb interlayer. The maximum strength of the joint is 205 MPa. However, an incomplete fusion defect can be observed at the Nb/Inconel 718 interface when the heat input is 34 J/mm, resulting in a tensile strength of 13 MPa.