Abstract: As a kind of basic operation, polarity conversion is largely involved in the polarity optimization of Reed- Muller (RM) logic circuits, especially for large-scale circuits. The rate of polarity conversion has a direct impact on efficiency of the polarity optimization. A mathematical model is established for area optimization of XNOR/OR circuits, which is a kind of basic realization of RM logic circuits. A novel polarity conversion technique is proposed by combining the superiorities of the existing ones. Based on the features of the novel conversion technique, an area optimization is proposed for large-scale XNOR/OR circuits. Experimental results show that compared to other conversion algorithms, the proposed polarity conversion technique can significantly improve the area optimization of XNOR/OR circuits.