Abstract: In this paper, the response surface method of Design-Expert V12 was used to design the compound active agent formula for TCA laser welding, and the effect of active agent on the weld penetration and forming coefficient of TC4 laser welding was studied. The result showed that based on response surface method, the designed \mathrmNa_2 \mathrmSiF_6 and \mathrmY_2 \mathrmO_3, \mathrmNa_2 \mathrmSiF_6 and \mathrmTiO_2, \mathrmY_2 \mathrmO_3 and \mathrmTiO_2 had positive interaction on weld penetration, and \mathrmNa_2 \mathrmSiF_6 and \mathrmY_2 \mathrmO_3, \mathrmNa_2 \mathrmSiF_6 and \mathrmTiO_2 had positive interaction on forming coefficient. TC4 titanium alloy was welded with optimized compound active agent, the weld penetration increased by 1.49 times than that of uncoated active agent, and the forming coefficient reached 0.494 . Compound active agent I could not only significantly refine the coarse columnar crystal of the weld, but also refine the \alpha, phase of acicular martensite within the grain. The width of the heat affected zone was reduced, and the forming quality of the weld surface was excellent. The tensile strength of welded joint was about 5.53 \% higher than that of the uncoated active agent, and the elongation after fracture was about 1.5 \% higher than that of the uncoated active agent.