Abstract: Probability vectors are employed to obtain a new fault-tolerant routing algorithm for the parallel m-ary n-cube networks. The k-level unsafe nodes SAk (1≤k≤n) should first be determined so as to compute this probability vectors, which means the distance failing to respond to communicative signal starting from the the source nodes, due to vertex or edge failure, is the destination node of k. The fault-tolerant routing and the probability vector algorithm are put forth after the unsafe node set SAK is determined.