本文使用因子分解(factoring)的方法计算网络的根通信可靠性(存在从根点到每一个其它结点正常运行道路的概率)。我们充分利用无圈有向网络的拓扑结构提出了两个新的可靠性保护缩减(Reliability-Preserving Reduction)和一个进行因子分解的选边规则。在此基础上,给出一个因子分解算法(factoring algorithm)。对于不是非常稠密的网络,该算法是非常有效的。 In this paper, factoring (factoring) method is used to calculate the root communication reliability of the network (there is a probability of running the road from the root point to each of the other nodes). We make full use of the topology of the ringless networks to propose two new Reliability-Preserving Reduction and one edge-factoring rule. On this basis, a factoring algorithm is given. This algorithm is very effective for networks that are not very dense.