In femtosecond pump-probe spectroscopy, spatial resolved probe signal reflects the nonlinear effects of the sample in different spatial positions. However, as the pump intensity increases, high order, especially fifth-order nonlinear effects will appear in the probe signal. The split-step method is used to directly solve the nonlinear propagation equation with one transverse dimension. In the numerical simulation, the effects of fifth-order nonlinearity in pump probe process are studied for different pump intensities and spatial positions. For sufficient intense pump field, the probe signal show distinct interference between the third- and fifth-order nonlinear polarization. Clearly oscillation has been observed in the signal. At the spatial position far away from the center of the pump field, the fifth-order contribution of the probe decays much faster than the third-order contribution. The physical mechanism and intention are discussed qualitatively.