Abstract: According to the limitation and shortage of the present detection work of composite insulators, the online automatic detection device for the hydrophobicity of composite insulators is developed. The device is composed of a water spraying device, a micro shooting device and a portable computer, which is equipped with hydrophobicity analysis software. Hydrophobicity analysis software is developed on the Matlab platform, using the advanced image processing technology and BP neural network to realize the automatic recognition of the hydrophobicity of insulators. The software has a database management function, which can query historical data and evaluate the test results. At the same time, considering the influence of seasonal variation factors on the hydrophobicity of composite insulators, a scientific evaluation method is established, and reasonable operation and maintenance plans and suggestions are given. The test results show that the device can be safely, quickly and accurately, and can automatically detect the hydrophobic grades of composite insulators, and the accuracy rate is more than 90%, which provides data support for technical personnel of power supply companies and meets the actual needs of engineering.