Summary: Scheduling optimization in re-entrant lines is proved to be more difficult than in other manufacturing systems, which is well known as an NP-hard problem. A mathematical programming model is established and corresponded with a digraph via several definitions for an intelligent algorithm. A hybrid algorithm is proposed to optimize the objective function, which takes the advantages of genetic algorithm and particle swarm algorithm, so this hybrid algorithm integrates global searching ability with high convergence speed. Compared to the results of the normal GA or PSO, simulation results show that the hybrid algorithm is an effective method for scheduling optimization.