Abstract: In order to deal with some unsolved problems in the engineering prototype design of a new electromagnet drive device for nuclear reactor control rod, the property experiment in view of principle prototype is carried out. Actual displacement of nuclear reactor control rod is measured by means of raster ruler and the test data is obtained by means of computer.The computer communicates with PLC using RS232 serial port.The experimental results show that the monitoring system have the properties of high reliability and high precision, and ensures the experiment to accomplish successfully.