Abstract: This paper presents a control system design method for a 5-DOF space docking simulation platform based on hierarchical finite state machine,and gives an extended definition for state machine.We add an aggregation of variables defined in the states,enabling the system code to be easily implemented.According to the fixed time interrupt which is gene-rated every 10 ms by the control system,we keep dividing the hierarchy of the state machine until we can analyze the states,transition,and inheritance between states in every 10 ms hardware interrupt service routine.The structure of the interrupt service routine will be more legible.Practical application of the system proves the validity of the presented method.