Progressive　collapse　is　a　mechanical　process　that　exhibits　nonlinear　and　dynamic　characteristics.　The　nonlinear　dynamic　effect　on　the　progressive　collapse　resistance　demand　can　be　accurately　evaluated　by　the　nonlinear　dynamic　(ND)　method.　In　engineering　practice,　however,　the　simplified　and　easy-to-use　linear　static　(LS)　method　is　often　adopted.　That　is　accomplished　by　using　a　dynamic　amplification　factor　(DAF)　to　correct　the　LS　resistance　demand　to　approximate　the　true　ND　resistance　demand.　In　this　paper,　the　analytical　expression　of　the　DAF　is　established　based　on　the　energy　conservation　principle.　The　collapse-resisting　substructure　is　firstly　simplified　as　a　single-degree-of-freedom　(SDOF)　equivalent.　Then　the　energy　conservation　equation　and　the　static　balance　equation　of　the　SDOF　equivalent　are　established　to　obtain　the　ND　and　LS　demands.　Finally,　the　DAF　is　obtained　by　dividing　the　ND　demand　by　the　LS　demand.　The　DAF　is　validated　through　a　series　of　the　numerical　examples　including　a　SDOF　system,　a　3-storey　planar　frame　and　an　8-storey　3-D　RC　frame　model　structures.