Many studies have proved that the role of magnetic ellipsoid of rocks is equal to that of tectonic strain ellipsoid. The parameters of magnetic fabric, such as P, T, F and L, can be used to describe the behaviors and periods of tectonic deformation. The features and periods of tectonic deformation of the Bobai-Hepu fault are studied with rock magnetic fabric in this paper. The research shows that the anisotropy parameters (P) of the Bobai-Hepu fault can be divided into three parts which stand for three types of tectonic deformation: brittle (P≤0.35),ductile brittle (0.40≤P≤0.60) and ductile (P≥1.0). The shape factor of magnetic ellipsoid (T) shows that the fault has two kinds of magnetic ellipsoids which are the compression (T<0 )and stretch (T>0). The relation between magnetic foliation (F) and lineation (L) shows that the fault has three types of strain which are plane, non plane and linear strains. The trends of the principal axes of magnetic ellipsoid show that the fault has been acted by the stresses with different direction in varied periods and has different shear trends. The final result of the present paper is that the Bobai-Hepu fault suffered three period tectonic deformation with varied deformation mechanisms.