According to the production characteristics of flexible job shop scheduling in practice, the initial solution is generated by random Numbers, Gantt chart is drawn, and the maximum process time is calculated. Then, a simplified algorithm is proposed with reference to Johnson's algorithm. Combining Johnson algorithm and least time principle and minimum principle, puts forward a simplified algorithm. Johnson algorithm applies only to the limitations of two machine scheduling, this simplified algorithm extends the algorithm performance, so the job-shop scheduling of multiple machines can also be calculated, and the simplified algorithm is applied to an example. By comparing the optimized algorithm with the initial random solution with the obtained data, the effectiveness and superiority of the algorithm can be seen.