Abstract: Aiming at the problem of corrosion detection of buried gathering and transmission pipeline under trenchless conditions, combined with magnetic dipole model and stress magnetization model, a forward modeling model of weak magnetic signal of defective pipeline was established. The waveform characteristics of magnetic induction intensity of corrosion defects and the effects of ground clearance and magnetization on magnetic induction intensity were studied by numerical simulation. The results show that at the corrosion defect B_Xand by had extreme value characteristics and opposite direction, B_Zhad zero crossing characteristics and the peak value changed direction. The effects of ground clearance and magnetization on the signal were discussed respectively. Finally, the field test was carried out to verify the accuracy of the forward model, and the error rate was 11.11%.