Abstract: In view of problem of bigger workload because of needing write control program individually for each automatic blending system of thermal power plant, the paper introduced design of a general coal blending control program. Taking coal plough as control object and finding association condition influencing on lifting and falling of coal plough, it designed general PLC function block. The actual application showed that the program has strong portability and expansibility and high reliability, which saves time of programming and debugging of coal conveying control system.