This paper investigated the microstructure and mechanical properties of Q235/304 stainless steel clad plate welding seam produced by hybrid welding of tungsten inert gas welding (TIG) and metal active gas arc welding (MAG). The results showed that the dual phases containing ferrite and austenite appeared in the stainless steel covering welding (SSCW), while the partial martensite phases appeared in the carbon steel backing welding (CSBW), which is attributed to the dilution behavior of Ni and Cr elements from stainless steel to the Q235 steel results into the movement of the CCT curve to the right side and the decrease of critical martensite formation cooling rate. The CSBW possesses the highest microhardness value in the weld metal due to the existence of the martensite zone. The impact tests were carried out and the results showed that the Charpy absorbed energy of weldments (81 J) is almost equal to that of base clad plate (83J). The SSCW layer possesses the ductile fracture characteristics accompanying many dimples. However, in the CSBW layer, some cleavage fracture characteristics are presented in the radiation zone while many dimples are located in the fibrous zone, revealing a complex combination of brittle and ductile fracture behavior, which is due to the existence of martensite zone, different stress states and crack propagation velocity. HIGHLIGHTS Hybrid (TIG, MAG) welding is suitable for welding stainless steel clad plate; The martensite formation in CSBW is related to dilution and diffusion of Cr and Ni; Partial martensite transformation can strengthen and toughen the welding seam.