In this paper we propose a secure and efficient off-line micro payment scheme. There are five par-ties in our scheme: Consumer, Bank, Merchant, Issuer and Trusted Authority. The coins are made by Bank in cooperation with Issuer to prevent not only Bank from impersonating a consumer to steal consumer’s money but also Issuer from making coins of his own accord. The representation of coins is based on hash chain tech-nique that the coin verification can be done quickly during a transaction. Furthermore, we propose a dual sig-nature scheme extended from RSA algorithm that a legitimate coin must be signed by both Issuer and Con-sumer to assure no one except Consumer can spend coins, and no coin can be expanded from any legitimate coin chain. In summary, our system has the following properties: (1) Unforgeability and Unexpandability of coins. (2) Efficiency of coins verification. (3) No-usurpation of coins. (4) Anonymity of Consumer. (5) Traceability of double-spender.