Aiming at high-speed arc-assisted laser welding of 0.5 mm pure titanium TA2 thin plate,the influence of heat source distance and relative position of laser source on laser-arc coupling and molten pool shape was studied. The high-speed photography was used to analyze the arc shape and molten pool shape and explore the effects of different heat source distances and relative positions of heat sources on the stability of high-speed welding of thin plates were investigated. The results show that the TIG arc area will increase with the decrease of the heat source distance in the two modes of laser source relative position（Laser Leading,LL and Arc leading,AL）;in the AL state,the arc plays a role of preheating,in the LL state,when the heat source distance is reduced to 6 mm,the laser and TIG arc work together to form the eutectic pool phenomenon;the standard deviation of the TIG arc area in the LL state is smaller,and the welding process stability in the LL state is better than the AL state.