Abstract: The size and distribution of microbubbles have an important impact on the separation efficiency of flotation processes, and the establishment of an easy-to-operate in-situ detection method that can be applied to complex scenarios is particularly important for the development and application of microbubble technology. In this study, an in-situ microbubble size measurement method based on high-speed camera technology was established, which was applicable to in-situ measurement of microbubbles in industrial scenarios and avoids morphological changes when the bubbles were removed. The results showed that minimum microbubble size recognized by this method was 7.2 μm, and the relative standard deviation was <5%, indicating that the developed method had high sensitivity and precision, and could be used for the in-situ measurement of microbubble system with large flow and high velocity. The size distribution of microbubbles in DAF process could be better fitted by the log-normal distribution. The microbubble size increased from 21.0 μm to 27.5 μm when the vertical distance between shooting position and releaser was increased from 0 to 13 cm, while the increase of the horizontal distance had little effect on the microbubble size. The microbubble size decreased with increased pressure (0.20~0.48 MPa), and when the pressure was greater than 0.32 MPa, the increase of pressure had no obvious effect on the microbubble size. Addition of sodium dodecyl benzene sulfonate (SDBS) led to a decrease of microbubble size from 26.4 μm to 21.4 μm, and the size distribution was more concentrated.