Abstract: Formation mechanism and its research progress in special 3-D net structure of waxy crude oil are introduced.Function of magnetic field on paraffin magnetic cores is analyzed.Paraffin control and viscosity reducing of crude oil with magnetic treatment are studied and experimented.Under the function of magnetic field, magnetic cores of paraffin orient in order of level and procession around magnetic field; function of magnetic field varies wax deposition course of paraffin in crude oil, which can effectively prevent wax crystal forming 3-D net structure, and makes the core radius of wax crystal minor, latent heat released from wax crystal increased so as to control wax deposition and reduce viscosity of crude oil.