Laser welding-brazing was developed to join dissimilar AZ31B magnesium (Mg) alloy and AISI304 stainless steel using a high power fiber laser. The maximum joint strength was 211 MPa, which reached 89.8 % of Mg base metal. The interface characterization and fracture behavior of the joints were investigated by employing optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. A transition zone was observed at the interface of fusion zone/steel, where the intermetallic compounds of Mg2Ni and Mg17Al12 were found. The offset from the center of laser beam to the edge of joint seam played a big role in the joining strength by changing the area fraction of reaction layer to whole interface. The smaller the laser offset, the larger the area fraction of reaction layer to whole interface, and thus the stronger the joining strength is. By the characteristics observed on fracture surface, the fracture behavior was summarized.K e y w o r d s : laser brazing, stainless steel, magnesium alloy, interface, tensile strength