The　traditional　separation　processes　of　metal　tubes　had　some　disadvantages,such　as　low　productive　efficiency,　high　energy-consumption　and　waste　of　raw　materials.　A　new　method　for　separating　tubes　was　adopted.　The　eccentric　loading　technology　and　stress　concentration　effect　were　used　to　promote　the　rapid　initiation　of　fatigue　cracks　at　the　bottom　tip　of　V-shaped　groove　and　control　the　steady　propagation　of　fatigue　cracks.　The　working　principles　of　fatigue　fracture　separation　device　under　eccentric　cyclic　loadings　were　described.　The　judgment　formula　of　crack　initiation　at　the　root　of　V-shaped　groove　of　tubes　under　fatigue　loadings　was　deduced.　The　four　experimental　control　curves　including　linear　decrement　control　curve,　multi-step　decrement　control　curve,　1/4　convex　arc　decrement　and　1/4　concave　arc　decrement　control　curve　were　designed.　The　304　stainless　steel　tubes　were　studied　by　experiments　under　the　control　curves,　finally　the　tube　precision　separation　was　achieved.　The　experimental　results　show　that　using　the　stress　concentration　effect　of　V-shaped　groove　and　the　continuous　action　of　eccentric　loading　forces,　the　loading　frequencies　are　gradually　reduced　from　high　to　low　by　using　multi-step　decrement　control　curve,　then　the　rapid　initiation　and　stable　propagation　of　cracks　at　the　root　of　V-shaped　groove　of　tubes　may　be　ensured.　Finally,　tube　fast　fracture　is　realized　and　good　cross-section　quality　is　obtained.　©　2020,　China　Mechanical　Engineering　Magazine　Office.　All　right　reserved.