Intelligent computer-assisted instruction(ICAl)system is a complex knowledge base system concerning many areas' knowledge.Ideal ICAl system should have strong adaptability in order to accomplish the goal of specialized education. Computational reflection is a kind of computing activity which causally refers to itself. Based on the concepts of computational reflection, this paper discusses a computational reflective model of knowledge base system, and applies this model into the design of ICAl system. Further more, a preliminary ICAl model containing teacher and student entities is presented. Each knowledge entity in the ICAl model consists of objective and reflective levels. In different levels, there are different tasks which depend on.different knowledge sources.