The paradigm of forward security provides a promising approach to deal with the secret key exposure. It guarantees that the compromise of current secret keys does not compromise past secret keys and past communications. Therefore, forward security can minimize the resulting damage caused by the secret key exposure. In this paper, we propose a new forward-secure identity-based encryption (FS-IBE) scheme which is forward-secure against adaptive chosen-ciphertext attacks under in the standard model. In the proposed scheme, some of the main efficiency parameters are independent on the total number of time periods. Compared with the existing FS-IBE scheme, our scheme is much more efficient.