Continuous fiber laser was used to carry out laser welding process experiments of dissimilar materials butt joints between 5083 aluminum alloy and TA15 titanium alloy with the same thickness of 4 mm. The morphology and composition of the microstructure were analyzed by scanning electron microscope (SEM), backscattered electron detector and energy spectrometer (EDS). It was observed that there were a large quantity of intermetallic compound phases with different microscopic morphologies and uneven distribution within the interface reaction zone when laser focusing on titanium side. Moreover, the reasons for the formation of different morphological characteristics were explain from thermal and mechanical aspects. Furthermore, tensile performance test was carried out under the normal temperature, and the fracture morphology was analyzed to determine the characteristics of brittle fracture. The fracture occurred in the TiAl phase at the interface, and the highest tensile strength was 150.73 MPa.