The effect of helium radiation on the heat transfer performance of tungsten was studied using molecular dynamics method. The changes of thermal conductivity of single crystal tungsten and polycrystalline tungsten with helium content as well as the microscopic mechanism were analyzed at the atomic scale. The results show that, as the number of helium atom increases from 0 to 500, the number of defect pairs in tungsten increases first and then decreases. When the number of helium atom in single crystal tungsten is 230, the defect pair reaches a peak of 123. In polycrystalline tungsten, the number of defect pairs reaches a peak of 124 at 480 helium atoms. The lattice structure of tungsten changes from bcc to coexistence of bcc, fcc and hcp. The thermal conductivity of tungsten fluctuates significantly with the increasing helium content, which shows a trend of nonlinear decrease in general. When the helium content is 0.75%, the thermal conductivities of single crystal tungsten and polycrystalline tungsten decrease by 1.44% and 1.3%, respectively. The creation and aggregation of point defects as well as the change of crystal structure induced by helium radiation are responsible for the decrease of thermal conductivity of tungsten.