In order to consider the effect of strength anisotropy on earth pressure, the shear strengths on different shear planes of compacted silty fill are measured by direct shear tests. It is proved that the relationship between shear strength parameters and the dip angle of the shear plane can be expressed by the elliptic function. On the basis of Rankine's assumption of earth pressure, assuming that the transverse isotropic fill behind the wall has a horizontal compaction surface, the expressions of the dip angle of the slip surface and the resultant force of active earth pressure are obtained by analyzing the force balance of sliding wedge in the active limit state. The analysis of the ultimate stress state of the fill behind the wall shows that the active earth pressure acting on the back of the wall is linear. Parameter analysis shows that considering the anisotropy of cohesion and the anisotropy of internal friction angle, the active earth pressure value is greater than that of isotropic fill. Compared with isotropic fill, the anisotropy of cohesion makes the slip surface steeper. In addition, considering the anisotropy of the internal friction angle, the steeper sliding surface will be obtained in the fill with a smaller internal friction angle, while the slower sliding surface will be obtained in the fill with a larger internal friction angle.