The permanent magnet induction stepping motor is complicated in structure w ith the ax ial and radial magnetic circuits made. The more effectiv e method for the calaclation is to combine the mag netic field w ith the magnetic circuit. The basic idea on t he met hod is discussed in this paper . The key calculation model of the method, the Tooth Layer Unit, and its eng ineering rationality are analyzed with the 2- D finite element algorithm adopted. The r esult shows that the method is simple and pract icable and that the calculation model can meet the precision reguirments in engineering.