Multi-Agent systems (MAS) generally exhibit complicated dynamic structure and b ehavior characteristics. If traditional architecture description languages (ADLs ) are applied, semantic gap and expression problems are difficult to overcome. A n agent-based architecture description language A-ADL is proposed in this pape r, which takes computation/connector agent as architectural elements instead of component/connector in traditional ADL. By introducing architectural primitives, rule-based agent description and multi-view mechanism, it can be effectively used to model complicated dynamic architectures and overcome semantic gap mentio ned above. This paper also describes dynamic architecture modeling method of A- ADL in detail with an example, and justifies the suitability of A-ADL for MAS b y comparing A-ADL with several other traditional ADLs.