以华能某电厂5号、6号300 MW直流炉机组为例，介绍了机组高低压旁路控制系统及其组成。针对控制系统控制功能落后、控制精度不高、现场单回路控制器老化等问题，采取改进措施，优化控制回路及逻辑，调整了控制参数，更换了现场单回路控制器，完善了连锁和保护功能。

This paper introduced the control system and composition of the high and low pressure bypass in No5 and No6 300 MW once-through boiler power generation units in Huaneng power plant as examples. There were some problems in this system, such as unsatisfactory function and accuracy of the control system, and aging single loop controller. It was necessary to take measures for these problems, which included optimizing control logic, regulating control parameters, replacing on site single loop controller, perfecting interlock protection function and so on.