Abstract: As the outer defects of long-distance oil and gas transmission pipelines affect the safe operation of the pipelines, a nondestructive testing method based on motion-induced eddy current (MIEC) magnetic field is proposed. With the help of ANSYS Electronics finite element analysis software, the relationship between pipe surface defect parameters, detection speed and the MIEC magnetic field is analyzed. The results show that under different pipe surface defect parameters, the MIEC magnetic field will induce different magnetic flux density signals according to the difference of defect shape and size. The larger the defect size is, the stronger the signal induction is. With the increase of detection speed, magnetic flux density of MIEC will gradually increase and its overall change trend is basically the same. According to the engineering practice, a pipeline nondestructive testing device based on MIEC magnetic field is developed and experimental research is carried out. The feasibility of this technology is verified as the experimental results have the same trend with the finite element simulation results. It can be concluded that the MIEC magnetic field nondestructive testing method can achieve accurate location and identification of pipeline defects.