The invention discloses an alloy powder and method for synchronously sending powder and welding a galvanized steel sheet and AZ91D magnesium alloy based on laser. A main component of the powder is AlMgxCuZn, wherein x is the mole ratio of Al and Mg, the ratio range is between 0 and 0.4, the size of the powder is 100 meshes to 300 meshes, and a process method which is matched with the alloy powder and method for synchronously sending the powder and welding the galvanized steel sheet and the AZ91D magnesium alloy based on the laser can improve wettability and compatibility between the galvanized steel sheet and AZ91D magnesium alloy. According to the alloy powder and method for synchronously sending the powder and welding the galvanized steel sheet and the AZ91D magnesium alloy based on the laser, the laser is taken as a welding hot source, under the protection of protective gas and the hot effect, a part of the surface of a material to be welded melts, through effective sending of the alloy powder, a stable weld pool is easily obtained, burning loss of alloying elements is reduced, the ratio of the alloying elements in a weld joint can be accurately controlled, a formula for filling the alloying powder is flexible, metallurgy action of weld metal can be remarkably improved, the weld joint without inclusions can be obtained especially aiming at the existence of Zn, a welding surface needs no special cleaning, welding efficiency is high, cost is low, the joint is reliable, and the alloy powder and method for synchronously sending the powder and welding the galvanized steel sheet and the AZ91D magnesium alloy based on the laser has relatively ideal engineering practical significance.