Abstract: Taking account of the bottleneck-path which results in the congestion of network and analyzing the reason of unbalanced load with the link cost redefined, a genetic algorithm (GA) is presented to solve the problem of multicast routing. The algorithm begins from a conversion of the weight of link cost with an initial solution set in terms of delay-satisfied multicast trees provided for GA, then the expensive tree links are substituted iteratively with the cheaper ones during the crossover operation so as to get the multicast tree satisfying delay constraint with lowest cost. Simulated results showed that the proposed algorithm is available to construct effectively and quickly, the multicast tree satisfying delay constraint and lowest link cost, with network load balance taken into account to pick out the cheaper idle route.