Abstract: 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.