Cigarette packet missing detection and elimination method and system

The invention discloses a method and a system for detecting and rejecting cigarette packet missing. The system comprises a packet missing detection device, a cigarette rejecting device, a PLC (Programmable Logic Controller) and a display screen, the time obtained through a first optical fiber probe and four metal probes of the packet missing detection device is subtracted, an absolute value is obtained, if all values are smaller than an allowable timing error, no packet missing exists, if any value is larger than the allowable timing error, it is considered that the cigarette packet is missing, and a cigarette packet missing signal is sent to the PLC; the PLC receives a packet missing signal and then sends the packet missing signal to the removing device, packet missing cigarette cartons are removed by rotating the convex lug belt reversely, if manual packaging is needed, a cigarette blocking air cylinder of the removing device is put down, the convex lug belt rotates forwards to push out qualified cigarette