Abstract: The CA （Concept Algebra）, founded by Prof. Nilsson and based on the lattice theory,is a new algebra system in its early stage. In CA, the,relational and OO paradigm,logic programming, and the frame formalism of knowledge representation are incorporated into one uniform representation form: concept term. Terms further comprise sentences, and a knowledge base is made up of such terms and sentences. Inference operations are represented as a group of algebraic axioms referred to as rewriting rules. At present, the CA is far from perfection, and remains to be extended. This paper surveys the CA and makes some basic extension.