Abstract: A model is established to study the transportation of particles along the surface of a microtubule, caused by some environment parameters in an ECR plasma system. In this model, the thermal fluctuations, the magnetic field and the external force are three driving factors for obtaining a net probability current J. When the three driving factors compete with each other, the current J may reverse its direction in view of the variation of some parameter. The current J is also obtained respectively as the function of different parameters.