Abstract: In order to study the effect of different welding processes on mechanical properties of stainless steel fillet weld connections, the monotonic tensile tests of 12 austenitic and 12 duplex stainless steel specimens were carried out. The results show that the failure surface of specimens made by TIG (Tungsten Inert Gas Welding) is quite different from that of specimens made by SMAW (Shielded Metal Arc Welding), and the latter is much smoother. Besides, the true failure angle of the transverse fillet weld connections is not the theoretical value of 45° due to the influence of the complex stress. For austenitic stainless steel, the strength ratios of specimens made by TIG to SMAW are 1.03 (for transverse fillet weld connections) and 1.13 (for longitudinal fillet weld connections), and the ratios of relative deformation are 1.46 and 1.11. For duplex stainless steel, the strength ratios are 1.12 and 1.04, meanwhile the relative deformation ratios are 1.66 and 1.45. The connections made by TIG show better mechanical properties. For the two stainless steel, the strengths of transverse fillet weld connections are much better than those of the longitudinal fillet weld connections, so it is suggested that the influence of the increase of the strength of transverse fillet weld connections be taken into account in the compilation or revision of the related specifications.