Composite detection technology. The compound of internal detection technology is an important development direction of current detection technology. Different types of internal detection technology such as intelligent diameter measurement, magnetic flux leakage, ultrasonic and inertial navigation are combined into the same internal detection equipment to obtain the most internal detection data resources with the minimum workload. The application of composite detection technology can effectively identify and quantify various kinds of composite defects in pipelines, and at the same time, through the fusion of multi-source data, it can improve the identification and quantitative ability of defects such as cracks and pinholes.