The mathematical model of laser cladding pool on titanium alloy surface was established using fluent software. The generation and development of molten pool under high intensity laser radiation are numerically simulated. The influence of laser irradiation time on the temperature field and flow field velocity distribution on the molten pool is analyzed. The width and depth of simulated molten pool and actual laser cladding channel was compared. The results showed that the temperature, flow velocity and geometric size of the molten pool developed rapidly within 0.1 second. And then the maximum temperature and maximum velocity of the molten pool tended to be stable after 0.2 second. The highest temperature is the surface center of the laser molten pool and the maximum fluid velocity is the surface edge. It is agree with the gaussian mode of laser energy source. Due to the heat loss and mass loss of the fluctuation and the splashing of the free molten pool, the width of the simulated molten pool is significantly larger than that of the actual melting channel.