The problem of task allocation in a multi-robot system may be defines as the problem of assigning a set of tasks into a number of robots with the goal of optimizing some performance parameters. However, when many requests are received simultaneously by a robot, the current scheduling approaches may make unreasonable decisions, delaying the execution of some requests and so affecting the system performance. This paper addresses this issue and proposes a new scheduling mechanism for task allocation in multi-robot system. The proposed approach implements a universal allocation based on Water Wave Optimization algorithm with the Genetic Algorithm (WWO_GA). The result of this approach is compared with the conventional Water Wave Optimization (WWO) and the Particle Swarm Optimization (PSO) algorithms. Simulation results show that the proposed approach improves the multi-robot system performance in terms of total traveled distance and computation time.