Abstract: Providing quality of service （QoS） guarantees in packet networks gives rise to several challenging issues. One of them is how to determine a feasible path that satisfies a set of constraints while maintaining high utilization of network resources. Multi-constrained QoS routing finds a feasible route in the network that satisfies multiple independent constraints. In general, multi-constrained path selection is an NP-complete problem that cannot be exactly solved in polynomial time. This NP-complete problem is converted into a multiobjective optimization problem with constraints. The background of multi-constrained optimal path selection is introduced first. A multiobjective QoS routing algorithm is then proposed to produce a set of nondominated optimal route based on the intelligent optimization principle of multiobjective genetic algorithms. The theoretic analysis and experiment results show that the genetic algorithm with multiple criteria is effective for multi-constrained QoS routing, and can play an important role in the performance of networks.