In view of the problems existing bubble detection and elimination methods of vacuum injection equipment, combined with machine vision and image processing technologies, the real-time monitoring method of bubbles is studied. Firstly, the direct image (DI) method is used to realize the vacuum injection bubble detection by CCD digital camera, and the continuous acquisition of bubble images is realized through VC++ thread technology. Then, the image processing algorithm suitable for vacuum injection bubble is studied, especially for the bubble feature extraction with high overlap and large distortion, a bubble edge pixel ratio calculation method is proposed, which better solves the problem of information loss of overlapping bubbles. Finally, the specific implementation process of the method is given, and its feasibility and effectiveness are verified through experiments.