A new multiconstrained routing algorithm based on quality of Service (QoS), DAG_DMCOP, is proposed. The algorithm is divided into two parts: (1) Pruning strategy. Find all paths that meet the needs of multiple constraints and convert the network topology into a Directed Acyclic Graph (DAG). (2) Search strategy. The link synthesis cost function is introduced to adjust the multiconstrained conditions (bandwidth, delay, delay jitter and other QoS parameters) adaptively. Then an improved Dijkstra algorithm is used to find out the optimal path that meets the needs of multiple constraints. Simulation show the algorithm can quickly find the path with the least cost and is suitable for large-scale multiconstrained routing networks. It is an efficient new algorithm for solving multiconstrained routing problems.