Abstract: In order to study the influence of hybrid heat sources on welding characteristics of T4003 ferrite stainless steel, the effect of parameters on the morphology and microstructure of laser-arc hybrid weld joints was investigated, and the range of the parameters were optimized. In addition, the impact toughness and enhancing mechanism of weld metal and heat affected zone at -40 ℃ were analyzed emphatically. The results show that the comprehensive mechanical properties of the joint under the optimization parameter are excellent: The tensile fracture occurred in the base material and the tensile strength is 530 MPa, and no crack is found in the 180° transverse bending tests. The average impact absorbed energy of weld metal(50 J) is slightly higher than that of conventional arc welding, and the average impact absorbed energy of heat affected zone is about three times of arc welding(32 J). The reason is that the low heat input of laser-arc hybrid welding refines the coarse grain in heat affected zone. Besides, the impact fracture morphology shows that the final fracture zone of weld metal mainly consists of dimples with no ductile-brittle transition, while the heat affected zone exhibited obvious ductile-brittle transition with quasi-cleavage morphology in the central expansion zone. This study can promote the application of laser-arc hybrid welding in ferritic stainless steel.