In this paper, a detailed analysis of the digital multi signature scheme and the improved multi signature scheme have been carried out. It points out that the forgery attack process which had been proposed by Zhang et al. cannot be established due to its parameter setting error, and the detailed proof has been demonstrated. A new sequential multi signature scheme enhancement is proposed by improving the existed parameters and adding new ones based on the intractability of discrete logarithm problem. A better security and effectiveness of this new scheme is presented in this paper as well, such as the resistance of forgery attack and the public key substitution attack, the satisfaction of non-repudiation and non-misuse, the property of identity identification, etc.