In　view　of　the　lack　of　a　general　method　for　calculating　the　cracking　loads　of　RC　beams,6　different　formulas　for　calculating　cracking　moments　were　first　compared　using　18　experimental　RC　beams.The　results　showed　that　the　deviations　between　the　calculated　and　experimental　cracking　moments　were　related　to　the　concrete　strength.Then　a　new　concept　of　plastic　deformation　development　coefficient,k,was　proposed　in　order　to　derive　a　new　cracking　moment　formula.The　formula　was　further　improved　based　on　k　and　the　influence　coefficient　of　plasticityγkrelated　to　k.The　recommended　values　of　k　andγk　were　given　according　to　the　concrete　strength.Lastly,12　experimental　RC　beams　were　used　to　verify　the　accuracy　of　the　improved　formula.It　was　found　that　the　estimations　by　the　improved　formula　agreed　well　with　the　experimental　measurements　and　was　more　conservative　than　the　existing　formulas.　©　2019,　Editorial　Office　of　Chinese　Journal　of　Computational　Mechanics.　All　right　reserved.