Abstract: The secret key exposure is a serious problem for the security of the digital signature. Unfortunately, for a regular digital signature, if the secret key is exposed, all the signatures previously signed are invalid because the verifier cannot identify whether a signature is produced before key exposure or not. Therefore, how to deal with the problem of secret key exposure in signatures is very important. Forward secure threshold signature is an important distributed signature to deal with this problem. It inherits the advantages of forward secure signature and threshold signature. The secret key is renewed periodically through the shares that the players hold, while the public key is fixed during the whole time periods. This kind of signature makes it more difficult for an adversary to compromise the security of the signature: if an adversary cannot attack a quorum number of players, he cant forge any signature; if an adversary can attack a quorum number of players in a certain time period, he cant forge any signature of previous time periods. In 2007, Peng et al. proposed a forward secure threshold signature scheme from bilinear pairing. Analyzed in this paper is the security of Peng et al.s scheme. Several techniques of security attack are given and it is pointed out that their scheme is insecure. At the same time, some improvement methods are also given.