The propagation of ULF waves （0.1—10 Hz） from magnetosphere to the conductive ground is studied in the presence of oblique magnetic field and the analytical solution is obtained. The effects on the parameters of the IAR, such as reflection coefficient, eigenfrequency and attenuation, are analyzed. It is shown by simulation that the change of oblique field results in the corresponding change of the scale length and the ionospheric conductivities. Along with the decrease of dip angle, the eigenfrequency declines and so does the attenuation of IAR. The conductivity corresponding to the maximum attenuation also decreases.