A dynamic architecture description must provide a dynamic behavior specification of software system. Based on the high-order multi-type π calculus theory, a dynamic architecture description language D-ADL is proposed. In D-ADL, components, connectors, and architecture are modeled as the ‘Abstraction’ type of high-order π calculus; system behavior is modeled as the ‘Process’; and the interaction point between component and connector is modeled as the ‘Channel’. D-ADL separates the dynamic behavior expressed in an explicit way from the computation behavior, which is helpful to edit and understand the changing logic in system. The result of the dynamic behavior can be beforehand deduced because this behavior is formalized as the high-order ‘Process’. On the basis of D-ADL specification, rules about applying the theory of behavior equivalence and behavior simulation in π calculus to online evolution and architecture refinement are proposed. How D-ADL can be used is illustrated through a case study.