On the basis of analyzing the requirem en t of pro cess control sy stem in chem ica l industry, the paper illustrates the pr inciple for realizing the pro cess con tro l system w ith adopting Programm ab le Log ic Contro ller ( PLC ) , g ives the flow chart, and introduces the signa l componen ts and dr iver of e lectrical equipm ents and the addresses o f I/ O connectors. It a lso illustrates how to se lect PLC and to w ire electr ica l equ ipm ents, g ives them ethod and concept for design ing state ladder graph ics o f PLC w ith log ica l design m ethod, presents the log ica l expression equations fo r every contro l step, and prog rams ladder graphics for realiz ing process contro .l As continuous con tro l and sequence contro l are used w ide ly in pro cess control sy stem s, the m ethod for control sy stem in this paper can be applied w ide ly.