Using particle image velocimetry (PIV),smoke flow visualization technology and Fluent software,shielding gas flow fields of coaxial powder feeder nozzle are researched in order to improve the shielding effect of gas flow on laser on-line rapid repair of aircraft structure damage. Influences of gas velocity from nozzle,crosswind velocity are systematically analyzed on gas impacting jet flow field. The results show that when the velocities of three-section gas flow are nearly consistent,the turbulent diffusion area disappears and a stable flow field can be obtained. When the gas velocity from center nozzle is smaller than that from outer ring,a vortex is generated and disturbs the stability of gas flow field. The crosswind produces prominent interfere to the gas protective range. With the increase of velocity of crosswind,the axis of shielding gas fields and nozzle get apart. When the velocity of crosswind surpasses 50% of the velocity of gas from nozzle,the shielding gas fails to protect molten pool totally because ambient air is mixed.