Abstract: In order to reject the slim cigarette wrapped with spliced cigarette paper, a new splice detector was designed for ZJ112A slim cigarette maker. On the basis of existing infrared photoelectric splice detector, a special optical lens was installed to focus the detection spot to less than 2 mm in diameter, a signal processing module was added to promote detection accuracy, and a visual display module was added to monitor the measured value of the infrared signal real-timely. The designed detector was tested with 36 bobbins of cigarette paper with purposely made splices. The results showed that any cigarette wrapped by spliced cigarette paper was detectable and rejected, no matter whether the splice was originated from the bobbin change or the bobbin, the rejection rate reached 100%. This technology provides a support for promoting cigarette quality.