In order to solve the problem that the current sequential function chart cannot express the conversion between automatic circulation and manual operation flexibly, taking the example of the typical work steps of hydraulic power sliding table as the research object, the paper brings forward a method by adding state variables and inserting some micro branches to hold the change process of dynamic memory between these two states. The sequential function chart and ladder diagram shows a more rigorous mapping relationship after redesign. By means of graph theory model establishment, we can find that the number of maximum flow has been increased than before after model reconstruction, but it still meets the needs of closure principle of graph, so as to maintain the stability of the control system. Through the observation of running the ladder diagram on the spot, the control program can shift between these two states with nondisturbance at the breakpoint, verifying the correctness and reliability of the new algorithm. 