This paper reports the systematic study of supporting forces and moving track of the ferromagnetic drug particulates in target therapy is performed using the electromagnetic theory. We have obtained the rules of action and effect of magnetic fields and blood stream and the walls of blood vessel on the ferromagnetic drug particulates. At the same time, we also give out the new method of magnetic drug targeting, namely, we make use of the magnetic navigating device located outside human body to produce the variable magnetic fields to realize magnetic drug targeting. The result of our research gives the conditions of carrying out magnetic medication target treatment.