Abstract: A part of Fushun-Bayuquan Products Pipeline is needed to be removed due to the urban planning of Yingkou City, Liaoning Province. While connecting the old and new pipe, magnetic blow occurred. Analysis showed that the generation of magnetic blow was caused by residual magnetic flux which yielded from internal inspection. The paper describes the principles and negative effects of magnetic blow. By simple but effective cable demagnetization method, the magnetic blow has been successfully eliminated.