In this paper, according to the analysis of control requirements, by Siemens PLC & MCGS configuration technology to achieve constant pressure and flow monitoring. The input and output signal of sensors is collected by PLC, and through PI closed-loop to achieve continuous control of electric valves, to achieve the purpose of pipe outlet parameters constant. Each device operational status be measured by PLC through a variety of sensors, and transmit the information to the host computer, the operational status of the equipment he monitored through curve forms by PC configuration software. When testing, the type of nozzle is XR - TEEJET110G2 from U. S spray company. When K = 0. 3,T =0. 04, the process value is coincident with the set value curve, the maximum control error is 0.01Mpa, and the output is almost no vibration* and the accuracy of pressure to 0. 01Mpa, the precision of flow to lL/mini shows that the system is reliable.%根据对控制要求的分析,采用西门子PLC+ MCGS组态技术来实现恒压、恒流监控功能; PLC用来采集传感器的输入/输出信号,并且通过PLC闭环PI控制的方式实现对QSVY型电动调节阀的连续控制,达到管道出口参数恒定的目的；PLC通过各种传感器测量各设备的运行状态,并把信息传送给上位机,上位机组态软件通过监控画面把设备的运行状态变化用动画、曲线形式表现出来;试验时,采用美国喷雾系统公司的XR-TEEJET11002型喷头进行控制系统的控制性能分析；当K=0.3,T=0.04时,过程值与设定值曲线基本重合,最大控制误差为0.01Mpa,且输出几乎不振荡,并可实现压力0.01Mpa的调节精度,流量1L/min的调节精度,说明本设计系统可靠.
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