To study the influence of different pulse parameters on the melting and resolidification behavior of tungsten after its temperature reaches the melting point under transient heat flow, the differences in morphology and structure of tungsten after melting and resolidification under IPEB (5 ms) and CPF (0.1 ms) were experimentally observed. The dependence of hierarchical structure and columnar crystal grain on pulse parameters was analyzed considering the driving force of molten layer motion, cooling rate, temperature gradient and other factors. The reason why the columnar crystal grains appear on tungsten at pulse width of 0.1 ms but not at pulse width of 5 ms was analyzed by calculating the thermal action characteristics for two heat sources. It is found that the beam with high current intensity and short pulse width is easy to promote the formation of hierarchical structure. The reason is that the high current intensity of the pulse beam can cause the molten layer motion on the surface of the material, while the short pulse width of the pulse beam can make the molten traces too late to recover and be quickly cooled and solidified. When the sample melts under transient heat flow, short pulse width is beneficial to the formation of columnar crystal grains and long pulse width is beneficial to the formation of equiaxed grains and grain growth.