This paper described two different kinds of claw pole motors used in automotive from structure and configure firstly, and then their characteristics and operation principle are introduced. By means of the powerful software ANSYS, the armature reactance of two motors are calculated through three-dimensional magnetic field analysis. Finally, on the basis of the calculation of the reactance parameters, the comparison of these two kinds of electric motors about synchronous and leakage reactance was done. The calculating result is accorded with the actual value.