The　ball　screw　(BS)　has　become　an　indispensable　key　functional　component　in　many　fields,　such　as　precision　manufacturing　equipment　and　intelligent　manufacturing　production　lines.　Inevitable　geometric　errors　and　non-constant　operating　conditions　affect　the　accuracy　decay　of　the　BS　component.　In　this　paper,　a　numerical　analysis　method　of　this　accuracy　decay　with　geometric　parameters　errors,　under　non-constant　operating　conditions,　is　established.　The　accuracy　degradation　of　the　BS,　under　a　single　non-constant　operation　condition　or　multiple　non-constant　operating　conditions,　is　analyzed,　using　a　proposed　numerical　analysis　method.　The　average　value　of　the　relative　error　between　numerical　analysis　and　theoretical　model　results　was　5.52%,　5.66%,　and　5.40%,　under　the　three　operating　conditions　of　non-constant　rotation　rate　(RR),　non-constant　contact　load　(CL),　and　non-constant　rotation　rate　and　contact　load　(RR　+　CL),　respectively.　And　the　maximum　relative　error　value　was　11.11%,　11.11%,　and　10.98%.　In　addition,　the　numerical　analysis　method　of　BS　accuracy　degradation　was　compared　to　experimental　tests.　The　average　value　of　the　relative　error　between　numerical　analysis　outcome　and　experimental　tests　was　7.07%,　6.08%,　6.56%,　and　the　maximum　relative　error　value　was　11.11%,　14.29%,　and　13.04%　under　the　three　operating　conditions　of　RR,　CL,　and　RR　+　CL,　respectively.