Thermal　fatigue　behavior　under　various　cyclic　heat　loading　is　an　important　concern　for　tungsten　as　armor　material　in　fusion　devices.　Surface　morphology　controlling　experiments　have　been　performed　on　polycrystalline　tungsten　using　an　ECR　plasma　system　and　cyclic　heat　loading　tests　have　been　conducted　upon　the　polished　and　modified　samples　using　an　electron　beam　apparatus.　The　results　indicate　that　the　surface　topography　has　little　effect　on　the　characteristics　of　damage　caused　by　the　cycle　plastic　deformation　during　the　cyclic　heat　loading.　The　micro-cracks　and　extrusions　form　in　some　grains　after　suffered　300　cyclic　heat　loading,　which　are　aligned　in　different　directions　for　varying　grains.　In　addition,　the　modified　specimens　with　both　different　triangular　pyramid　and　homogeneous　nanostructures　were　fabricated　by　dry　etching　under　different　conditions.　The　cross-section　of　damage　regions　were　analyzed　and　a　set　of　schematic　diagram　was　presented　to　explain　the　mechanism　for　the　formation　of　micro-cracks　and　extrusions　under　cyclic　heat　loading.