Abstract: In order to find a solution to the barcode errors on cigarette case possibly occurred during barcode printing and barcode label application, a PC-based real-time on-line barcode monitoring system was designed, in which a barcode scanner cooperates with sensors and WinAC, and the software for PC-based control is adopted to carry out barcode scanning and identification, cigarette case rejecting and data statistics. The real-life application showed that the average numbers of missing coding and hash coding reduced from 5 cases/month and 1 case/month to zero, and the system ran steadily.