The work aims to solve the problem of low efficiency and instability in manual inspection of bottle mouth quality. An STM32 hardware detection system based on 70 MHz frequency was designed with the HD video image technology of HD-SDI. Through the design of the hardware circuits, such as video read-in, 256 MB storage and 29.97 frame video input and output and alarm, a series of software algorithms for video processing, communication program and image processing were built to realize the defect detection of bottle mouth. The reliability of the system was analyzed by comparing the edge profile of plastic bottle mouth in a single photo. Experiments showed that the system could identify one bottle mouth in 0.26 s, and the output speed of the production line was 2.4 s/pcs. The system can stably detect the effect of various bottle mouth defects in real time.