Frequencyconversion traction locomotives are commonly used in tunneling in China. With the growing of the tunneling speed, more materials are to be transported in tunneling, which requires that the locomotives should have greater traction force. In this article, the existing control system of the locomotives and the requirement of the reconnection control system on the signal transmission and data processing of the reconnection control system are analyzed, and a reconnection control system is designed for a 40 t locomotive and a 20 t locomotive based on existing PLC control system, so as to improve the traction capacity of the locomotives. The reconnection control system designed has many advantages, which improves the tunneling efficiency and the equipment availability, reduces the construction cost and shortens the tunneling period.