In this paper, the typed category theory is extended and combined with process algebra to provide a unified description framework for the formal semantics of architecture-centric model transformations. The structural semantics of architecture models are described within typed category diagrams, and the behavioral semantics are represented by process traces affiliated to the categorical framework, and the mapping relations between component models are formally described by morphisms and functors of category theory. The framework can be used for the description, analysis and judgment of property preservation of model transformations, and thus make an effective support for model-driven software development.