The invention relates to a zero-gap galvanized steel sheet spliced joint laser welding method which is characterized by including the steps: firstly, providing a first workpiece and a second workpiecewhich need to be welded in a spliced manner; secondly, vertically splicing and clamping the first workpiece and the second workpiece; thirdly, providing a laser self-fusion welding system; fourthly,providing a laser filler wire welding system; fifthly, starting the laser self-fusion welding system; sixthly, starting the laser filler wire welding system, performing filler wire welding by a secondlaser welding head and a wire feeding head along a track of a first laser welding head to finish a welding process. The second laser welding head, the wire feeding head and the first laser welding head are serially arranged to form a column in a welding direction, the first laser welding head focalizes to form high-energy laser beams, and the laser beams vertically irradiate the surface of the first workpiece. The invention further discloses a zero-gap galvanized steel sheet spliced joint laser welding system. Compared with the prior art, the method has good welding effect and is simple in process.