Abstract: An internal detection system of stress concentration of an oil and gas pipeline based on unsaturated orthogonally magnetization is provided. The system comprises a detection device and a processing device; the detection device comprises a detection probe; the detection probe comprises a magnetizing device and a magnetic signal acquisition device; the magnetizing device is fixedly connected with the magnetic signal acquisition device; the magnetizing device is configured to magnetize a pipeline to be detected, so that the pipeline generates a magnetized magnetic field; the magnetic signal acquisition device is configured to acquire a magnetic signal of the magnetized magnetic field to obtain an acquired signal and send the acquired signal to the processing device; the processing device is configured to receive the acquired signal and obtain a stress concentration area of the pipeline based on the acquired signal.