ing at depth test of pipeline inwall defects, we propose a method of measuring the depth of pipeline defects, which based on the active thermal excitation by eddy current and infrared thermography. The theory of infrared imaging pipeline defects measuring is described. According to the special requirements of buried pipeline detection, a test device of eddy current thermal excitation with adjustable parameters is designed. Some specimens are fabricated according to the shape of the pipeline. With the active thermal excitation experiment based on eddy current, the influences of three important parameters, such as resonant frequency, lift-off distance and input electrical power on thermal excitation efficiency are analyzed, and the optimized values are obtained. Based on the above work, the infrared images of specimens with pre-designed defects which have different depths are acquired. The thermal image data analysis shows that the difference of grayscale between the defects and the non-defective areas varies with the defect depth, and the two factors show a single value correspondence, which has a good linearity under certain conditions. The defect depth detection model of groove-like and circular defects are established by the law. The experimental results show that the established model has certain detection accuracy. The research results show that the depth of defect can be calculated by infrared thermal image under the optimized active eddy current excitation condition. The proposed method based on active eddy current excitation of infrared thermal imaging pipeline is feasible.