Abstract: The drift of particle guiding centre in inhomogeneous magnetic field is discussed by making use of the average magnetic force on an equivalent circular current loop,and a model for Larmor gyration of a charged particle.Consequently two drift speed components perpendicular to the magnetic field is presented through the way of three-dimensional vector arithmetic,including the familiar term of grad B drift and an extra drift term caused by▽×B,which will be helpful to realize the drift instability of the high temperature fusion in magnetic confinement.