Abstract: Reduction of Attribution based on rough set theory is an important but difficult task under incomplete decision-making table. Information entropy and conditional information entropy are defined to express indispensable of attributes under incomplete decision-making table, a heuristic Algorithm based on conditional information entropy for reduction of attribution is proposed. By introducing relatively positive region, problem of redundant attribution created in the course of reduction of attribution under inconsistencies system can be resolved effectively. The complexity of this algorithm is also analyzed. Finally, an illustrative example analysis shows that this algorithm can find the minimal relative reduction for decision-making tables.