Abstract: In order to study the flow behavior of molten pool surface in the process of dissimilar steel gas tungsten arc welding, based on the particle tracing method, the flow behavior of the molten pool surface during the welding process of 304 stainless steel/Q235 carbon steel and 316L stainless steel/Q235 carbon steels were studied by the laser reflection on the molten pool surface. The movement trend of tracer particles on the molten pool surface was analyzed, and the flown velocity of molten metal on the molten pool surface was calculated. The results shown that the liquid metal flows from the stainless steel side to the carbon steel side during the TIG welding process, and the average flow velocity of tracer particles on the molten pool surface of 304 stainless steel/Q235 carbon steel was about 25.3 mm/s, and the average flow velocity of tracer particles on the surface of 316L stainless steel/Q235 carbon steel was about 21.6 mm/s.