Abstract: The requirement and implementation of data security in multi\|agent systems are discussed in the paper.To make itself intruder\|proof,a multi\|agent system must run on encrypted channel and provide the mechanism of multi\|layer authentication.Here presented is a method to ensure the security,which first provides low level signature and data encryption based on RSA algorithms,and then constructs a high level distributed security mechanism （DSM）.In DSM,the approach to access control is put forward.The agent can access the default services of another agent by its identification for flexible security configuration.