Abstract: This paper describes the application of magnetic technique to the production and transport of petroleum since the advent of neodymium-iron-boron (Nd-Fe-B), a permanent magnetic material with high magnetic energy product, magnetizing treatment of crude oil was carried out by a cohesive strong ma.gnetic field, resulting in an average viscosity-reduction up to 40～55%, the transpoitability was increased by more than 10%, and the paraffin removed interval for an oil well was prolonged from 10 to 20times. A correlation of the energy of the strong magnetic field to the change in shear force was derived in accordance with the principle of energy transformation. It is considered that viscosity-reduction lies principally in the change of shear force in crude oii under the effect of the strong magnetic field.