The　denial　between　the　original　signer　and　the　proxy　signers　is　a　serious　problem　in　multiple　grade　proxy　signature　scheme.　In　order　to　solve　this　problem,　an　undeniable　multiple　grade　proxy　signature　scheme　is　proposed　based　on　the　study　of　the　discrete　logarithm.　This　scheme　puts　a　private　key　of　the　last　proxy　signer　into　the　final　proxy　signing　key　to　ensure　that　none　of　the　signers　can　deny　their　signatures,　because　the　original　signer　and　the　proxy　signer　can＇t　produce　an　effective　multiple　grade　proxy　signature　by　themselves.　Therefore,　they　are　both　responsible　for　the　signatures.　As　a　result,　compared　to　other　schemes,　a　more　secure　multiple　grade　proxy　signature　is　achieved　with　this　solution.