Abstract: The detecting system of cartoner (CT) in GD packing line fails to exactly identify the cartons with appearance defects,therefore,a carton detector was designed with photoelectric and laser detection technology. The conveying and folding of carton blanks were monitored by optical fiber sensor and digital laser sensor separately,the carton with defective appearance resulted from carton blank misalignment was online rejected. And PLC was adopted for the functions of defective carton rejecting,machine stopping and alarm information displaying. The results of application showed that the detection rate for faults in carton blank conveying and folding reached 100% and 99.6%,respectively;the detection precision for carton appearance defects increased from 350 to 3 mm,and the packing quality was effectively improved.