A　new　uniaxial　tensile　fatigue　testing　system　was　set　up　by　the　use　of　a　micro-mechanical　fatigue　testing　machine　and　an　optical　microscope　for　thin　film　specimen.　The　mechanical　and　fatigue　behaviors　of　single　crystal　silicon　(SCS)　thin　film　with　V　shape　notch　were　studied　under　cyclic　fluctuating　loading.　Comparison　of　the　fatigue　testing　data　for　the　notched　SCS　thin　film　and　the　smooth　SCS　thin　film　shows　that　the　resisting　ability　to　bending　moment　and　fracture　stress　of　the　notched　SCS　thin　film　are　obviously　decreased,　and　the　failure　behavior　is　similar　to　that　of　the　macro　silicon　material.　SEM(scanning　electron　microscope)　fractograph　analysis　for　the　smooth　SCS　thin　film　and　the　notched　SCS　thin　film　showed　that　the　brittle　fatigue　failure　behavior　is　evidenced　by　the　brittle　fatigue　stripes　on　the　fracture　surfaces　of　both　kinds　of　SCS　thin　films　under　cyclic　fluctuating　loading,　and　the　characteristics　of　surface　are　related　to　the　structure　of　SCS.