With the convenience and development of digital signature and network technologies, several companies are beginning to transmit documents and messages over networks.This is expected to reduce costs and improve the efficiency of the working process. Based on the typical digital signature technique over public key infrastructure, each company can apply for its own certificate from the certificate authority to enable people to verify whether a message is signed by the company through the public key within the certificate. Generally, a general manager is responsible for signing a message to be published. However, the general manager is not always available; hence, the proxy signature scheme can be an efficient solution to this problem. In the typical proxy signature scheme, the delegator will delegate a proxy agent with the power of signing. The proxy agent can sign and produce the signature of the company on behalf of the general manager. A malicious proxy agent involved in the signing process may cause substantial damage to the company because of misbehaviors, such as signature forgery. Therefore, we propose a provably secure multi-agent designated proxy re-signature scheme. In the proposed scheme, the general manager designates several agents as delegatees. Each delegatee signs the message and send her/his signature to the proxy. The proxy can re-sign the message to form the signature of the company only when the proxy has obtained signatures from all delegatees. In addition, security definitions and formal proofs are provided in our scheme.