In　this　paper,　we　propose　a　novel　numerical　approach　to　construct　unconditionally　energy　stable　schemes　for　the　modified　phase　field　crystal　(MPFC)　model.　The　new　technique　is　based　on　the　invariant　energy　quadratization　(IEQ)　method.　The　numerical　schemes　based　on　IEQ　approach　lead　to　time-dependent　dense　matrices,　thus　the　fast　Fourier　transform　(FFT)　is　difficult　to　be　applied　to　solve　the　systems　directly.　By　introducing　a　new　auxiliary　variable　to　replace　the　original　one,　we　derive　a　novel　equivalent　MPFC　system.　A　step-bystep　solving　approach,　termed　3S-IEQ　method　is　considered　to　solve　this　equivalent　system.　Some　totally　decoupled,　linear　and　unconditional　energy　stable　semi-implicit　schemes　based　on　3S-IEQ　method　are　very　easy　to　construct.　More　importantly,　the　phase　function　phi　and　auxiliary　variable　eta　can　be　calculated　step-by-step.　Meanwhile,　the　proposed　approach　only　needs　to　solve　linear　equation　with　constant　coefficients　which　is　easy　to　use　FFT　directly　in　calculation.　Some　numerical　simulations　are　demonstrated　to　verify　the　accuracy　and　efficiency　of　our　proposed　schemes.　(C)　2021　IMACS.　Published　by　Elsevier　B.V.　All　rights　reserved.