Abstract: Most methods for attribute reduction in Rough Set model is based on static information system nowadays. However, data in real decision table changing dynamically. For dealing with such data effectively and efficiently, we first introduce incremental mechanisms for relation matrix and then develop an incremental algorithm for attribute reduction based on modified equivalence relation matrix. by which minimal attribute reduction of new decision table can be obtained quickly when when attribute values are Coarsened. Finally, Example confirms the feasibility and effectiveness of proposed operation and method of attribute reduction.