Abstract: In order to prevent the packets with defects of tear-tape missing or positional deviation from going into downstream machines, a tear-tape detector was designed and added to YB95 carton overwrapper.The detector was composed of tear-tape sensor, shift register, alarm and PLC.The tear-tape sensor monitors the position of tear-tape on film and releases a signal when a carton with tear-tape defects was found, and the controller would real-timely track the defective carton.When the defective carton reaches the outlet of YB95, the controller releases an alarm signal to remind the operator to deal with the defective carton timely.The practical application indicated that comparing with 2007, the number of defective carton went into downstream process for case sealing in 2008 reduced by 98.6%.