The fabrication of aluminum alloy complex components by using laser additive manufacturing process can satisfy the material-structure lightweight and improve the bearing performance. The solidification range of 7075 aluminum alloy is so large that the crack defects are easily caused due to the rapid solidification process of LPBF. And it is seriously limits the application of this alloy. In this paper, the LPBF process was applied to print the 7075 aluminum alloy, and the forming characteristics, solidification and crystallization behaviors, microstructure and properties were analyzed. The influence of melting mode on the microstructure and properties was also studied. In the high scanning speed range (800~2 400 mm/s), there are many cracks and porosity defects existed inside the alloy, and the microstructure is mainly coarse columnar crystals. When the scanning speed is 400 mm/s, the defects are disappeared. With the decrease of scanning speed, the melting mode gradually changed from heat conduction mode to keyhole mode, and the grain size was significantly refined. The mechanical properties of printed parts were greatly improved, and the tensile strength and elongation were 329 MPa and 11.2%, respectively.