The estimate of sniper rifle barrel deformation under solar radiation highly depends on accurate convective heat transfer coefficient. Based on a certain sniper model, a transient thermal fluid-solid interaction calculation model of a sniper barrel and nearby air had been built in CFX and ANSYS. The convection heat flow field around barrel, temperature variation and final deformation of barrel within 3 hours were obtained. Calculation results showed that there was obvious convection flow around barrel under solar radiation, complex turbulent air flow would be formed under continuous upper hot flow, this affected convection around barrel. The bending angle at barrel muzzle could reach 0.3mil under the coupling effect of temperature difference resulting from solar radiation and the barrel weight itself, which had obvious effect on shooting accuracy of sniper rifle. So the results will provide a numerical prediction solution for the sniper barrel deformation under solar radiation.