In order to explore the feasibility of low-power laser welding of steel and aluminum, a fiber laser was used to conduct laser brazing experiments of aluminum on the top and steel on the bottom with 1 mm thick 6061 aluminum alloy and 1.2 mm thick DP600 dual-phase steel as the test objects. The effects of laser power and welding speed on weld quality (joint formability, weld microstructure and mechanical properties) were investigated. Results show that the tensile strength of the joints first increases and then decreases with the increase of laser power and welding speed. The maximum tensile strength of the welded joint is 127 N/mm, the fracture shows typical brittle fracture characteristics, and the thickness of intermetallic compound is about 10 μm, under the laser parameter with power of 405 W, welding speed of 5 mm/s. The study provides certain technical support for improving the quality of laser welding. The effects of laser power and welding speed on joint formability, weld microstructure and mechanical properties esults show that the tensile strength of the joints first increases and then decreases with the increase of laser power and welding speed.