Abstract: Binary decision diagram (BDD) and Boolean satisfiability (SAT) are common techniques of logic circuit-based Boolean reasoning scheme.Since circuit-width is a good measure of circuit complexity,in this paper,we present a circuit-width based heuristic,which can be used to integrate the BDD technique and SAT technique for Boolean reasoning.The scheme switches one engine to another in terms of the circuit-width,thus it takes both advantages of these two engines.The circuit-width directed Boolean reasoning algorithm avoids the potential memory explosion caused by constructing the BDDs, and also prevents from the time-outs phenomenon of SAT techniques.In comparison with the previous heuristic schemes in literature,the new schemes can save more computational resources,and improve the performance of Boolean reasoning algorithms.On the automatic test pattern generation of combinational circuits,the experimental results demonstrate that the proposed heuristic scheme can be applied in Boolean reasoning effectively.