Firstly, genetic algorithm optimization method was put forward to solve optimization problems of sequencing in actual mixed model passenger car factory assembly line. Then genetic algorithm optimization methods and procedures of mixed model total assembly line production sequencing were studied. Finally, according to the characteristics of the mixed production line, the least total waiting time of vehicle was set to complete assembly as a sequencing optimization objective, the AutoMod simulation software was used to balance the allocation of resources and optimize the sequence by way of genetic algorithm, and the optimal sequencing solution was obtained. After optimization and balance, the total waiting time of mixed model vehicles in complete assembly line was reduced by 69.5%, which improves production efficiency greatly. This also proves the effectiveness of genetic algorithm optimization.