Abstract: Through simulation optimization and experiment, a set of inner wall damage detection system for pressure pipeline was developed, which was composed of low-frequency electromagnetic sensor module, signal generation module, power amplifier module and signal conditioning module. The pipeline is magnetized by low-frequency electromagnetic sensor and the electromagnetic signal of the pipeline is collected. The excitation coil is excited by the signal generation and power amplification module, and the data amplification and filtering were completed by the signal conditioning module. Finally, the pipeline internal defect detection is realized. The experimental results showed that the low frequency electromagnetic detection system can effectively detect the internal defects of 304 stainless steel pressure pipe with diameter of 152 mm, thickness of 16 mm and buried depth of 12.8 mm, and the optimal detection frequency was 100 Hz~200 Hz.