A numerical model of velocity distribution of shielding gas-metal powder two phases flow field output from the nozzle in laser cladding is established, and it is calculated by FLUENT software. In this model, the influences of momentum and mass transmission on the two phases flow are taken into consideration. The metal powder flow field velocity distribution on horizontal and center line is analyzed, as well as the velocity vector distribution of powder flow inside or outside the nozzle. The results show that powder velocity magnitude on center line increases first, then decreases, finally it keeps linearly increasing from the stand-off distance 100 mm below the nozzle; powder velocity magnitude on horizontal line reaches its maximum near the center line, then linearly decreases to 0 from the radial distance 6 mm to 11 mm. Under the same process parameters, the same flow field is measured with digital particle image velocity (DPIV) technique. The calculated result agrees well with the measured result, which indicates that the established model is reliable. The model can be used to obtain flow field parameters and further design the nozzle size.