Abstract: An enabling service platform based on web services was introduced. This platform was designed for medium-small scale enterprises allying dynamically for their business processing. The security threats to it were analyzed. A set of security mechanism suited for the platform was proposed. According to the mechanism, the function such as information security, access control, digital signature, authentication and intrusion detection were provided. In the mechanism, AES and chaos-based stream cipher algorithms were applied for data encryption. RSA algorithm was applied for both digital signature and key exchange. Guillou-Quisquater protocol was applied for authentication and a RSA-based secrete-sharing scheme was proposed for key storage. Neural network, data mining and computer immunology-based methods were incorporated in the intrusion detection system. The security of the mechanism was analyzed.