To　analyze　large　deflections　beams　in　compliant　mechanisms,　based　on　the　Pseudo-Rigid-Body　Model　(PRBM),　a　4R　PRBM　model　was　proposed　for　the　large　deflection　beams　with　single　inflection　in　compliant　mechanisms.　The　characteristic　radius　factors　of　the　model　were　determined　via　optimization　with　minimum　difference　of　inflections　and　the　spring　stiffness　coefficients　of　the　model　were　obtained　by　using　a　linear　regression　technique.　The　numerical　result　shows　that　both　the　tip　locus　and　inflection　point　of　the　compliant　link　with　single　inflection　can　be　simulated　precisely　by　using　the　model　proposed　in　this　paper.　©　2015,　Beijing　University　of　Technology.　All　right　reserved.