Conventional　PWR　fuel　only　needs　to　consider　the　single　heterogeneity　between　fuel　rods,　but　FCM　fuel　also　needs　to　consider　the　double　heterogeneity　between　particles　and　matrix.　Disadvantage　factor　method　is　a　typical　method　to　solve　double　heterogeneity.　But　there　are　still　some　problems　in　this　method.　Firstly,　the　equivalent　model　for　calculating　the　disadvantage　factor　is　established　by　the　conservation　of　volume　weight,　which　introduces　the　assumption　that　the　particles　are　uniformly　distributed　in　the　infinite　matrix　and　cannot　consider　the　macroscopic　heterogeneity.　Secondly,　the　disadvantage　factor　in　the　non-resonace　energy　region　is　obtained　by　ensuring　the　conservation　of　first　flight　collision　probability　in　the　3D　penetration　model,　but　this　method　cannot　meet　the　requirements　of　high-precision　calculation　in　FCM　fuel.　To　solve　these　problems,　this　paper　proposes　an　improved　disadvantage　factor　method　based　on　the　previous　work.　The　improved　disadvantage　factor　method　mainly　makes　two　improvements　on　the　traditional　method.　Firstly,　equivalent　one-dimensional　sphere　model　based　on　the　Dancoff　factor　replaces　the　volume-weight　equivalent　model.　Secondly,　in　the　processing　of　non-resonance　energy　range,　eigenvalue　calculation　is　used　in　the　new　model　to　obtain　multi-group　disadvantage　factors.　This　method　was　implemented　in　NECP-X　and　verified　in　different　working　conditions　and　problems　of　different　scales.　All　the　results　are　in　good　agreement　with　the　reference　solutions,　which　proves　that　the　proposed　method　can　effectively　deal　with　the　double　heterogeneity　in　FCM　fuel　and　obtain　accurate　effective　multi-group　cross　sections.　©　2022,　Editorial　Board　of　Atomic　Energy　Science　and　Technology.　All　right　reserved.