Force　measurement　is　indispensable　in　vast　engineering　applications　but　conventional　force　sensors　usually　encounter　large　measurement　errors　or　high　costs.　To　address　this　problem,　we　develop　a　force　sensor　based　on　a　3D-printed　elastic　ring　structure,　which　measures　the　external　force　by　utilizing　the　displacement　variation　of　the　elastic　ring.　The　nonlinear　theory　based　on　the　minimum　potential　energy　principle　is　proposed　to　describe　the　nonlinear　relationship　between　the　external　force　and　the　ring　top　displacement.　The　feasibility　of　the　proposed　force　sensor　scheme　is　validated　through　FEM　simulations　and　experiments.　The　range　of　the　force　sensor　can　be　adjusted　by　tuning　the　geometric　parameters　and　the　material　parameters　of　the　elastic　ring,　while　the　force　sensor　shows　good　measurement　error　at　different　measurement　ranges.　This　force　sensor　possesses　simple　fabrication　and　low　cost,　showing　good　potential　for　various　applications　such　as　industrial　automation,　mechanical　testing,　and　medical　devices.