Abstract: Degree-constrained QoS multicasting routing is important in communication network. A genetic algorithm is proposed for solving the problem. The method of forming a path by connected node is employed to design a Steiner tree representation. The crossover and mutation operators that can carry out the evolution of chromosomes with tree structure, and the method of modifying degree of nodes are designed. Numerical simulation results show that the algorithm has the capability of finding optimal solution. It is suitable for a large-scale network to solve degree-constrained QoS multicasting routing problem.