In this paper, we present a class-based object-oriented programming methodology - the Agent Class Methodology (ACM), a new kind of autonomous object generation methodology. The ACM specifies how to construct general-purpose agents that can be used to construct a communicating, distributed, concurrent system. Here we explain the ACM's autonomous control mechanism together with the four-layered-class inheritance architecture of agent class. And we also describe the features of agent class to demonstrate that the ACM meets with the basic features of object-orientation. As showed by our application of ACM, the traditional object-oriented programming technique can be promoted to an agent-oriented counter-part by the use of ACM.