Considering the many-to-many corresponding relationship between the assembly stations and the rail vehicles，the master program structure based on state information was designed. According to the working characteristics of the PLC，the state refresh method was used to obtain the state information，reducing the number of queries from conventional M×N to M+N. For the station with some special restrictions，a parallel positioning instruction given method was proposed and then realized through the example of automatic press station. The analysis shows that the total positioning time is approximately equal to the maximum value of the three axis positioning time. The electric monorail system runs well and completes the assembly positioning successfully in the field，showing a good engineering practical value as a result.