变换化简法是一种通过计算逻辑网络中门或连线处的最大允许函数集来消除网络中冗余门或连线的多级逻辑优化算法。文中提出了一种新的计算门处最大允许函数集的方法。该方法通过计算逻辑网络中门处的可观测性无关项较为容易得到最大允许函数集。实验结果表明，该方法在计算时间上明显优于原来的计算方法。 Transforming and simplifying method is a kind of multi-level logic optimization algorithm that eliminates redundant gates or wires in a network by computing the maximum allowed set of functions at gates or connections in a logic network. In this paper, a new method to calculate the maximum allowable function set at the gate is proposed. This method is easy to get the maximum allowable function set by calculating the unobservable observables in the gate of logic network. Experimental results show that this method is obviously superior to the original method in terms of computation time.