According to the theory of cigarette filter rod glycerol spray, the glycerol spray system uses PLC and touch screen as the main controller and consists of glycerol case, controlled temperature subsystem, glycerol spray subsystem, spray valve and servo systems. This paper studied the servo systems to make the valve position precise, and this technology can realize the tracking of the speed of the running tow in real-time. The PLC(Programmable Logic Controller) created the high-speed pulse trains, which correspond to the valve position and are used by the servo systems as the given displacements. Three closed loops of position, speed and current PID(Proportion Integral Differential) control were constructed to make the valve position precise, thus realizing the uniform spray of the running tow and ensuring glycerol spray in quantity eventually, as shown in the PLC control program flow charts. The system test results have shown that the system operates reliably and the hardness of the filter-rod has reached national standard.