Change impact analysis is useful in software maintenance and evolution. Many techniques have been proposed to support change impact analysis at the code level, but little effort has been made for change impact analysis at the architectural level. An approach is presented to support change impact analysis at the architecture level based on architecture slicing technique. The main impact of the reported approach is to assess the effect of changes in a software architecture by analysing its formal architectural specification, and therefore, the process of change impact analysis at the architectural-level can be automated completely.