Distribution of powder stream from coaxial nozzle directly affects the quality and accuracy of the parts by laser manufacturing. The convergent distribution of powder flow and powder convergent performance is researched. A theoretical model of coaxial powder nozzle is established. And a detecting system of powder stream field is developed to real- time measure morphology and concentration distribution of powder stream. The results show that the simulations of the powder flow agree well with the experimental measurements. The systemic studies on the behaviors of powder stream morphology and concentration distribution of powder stream help to optimize the design of coaxial powder feeding head and control laser manufacturing better.