Objective: To study the effect of resonance and non-resonance wave-matter interaction on the behavior of dispersion, absorption, and population inversion as a component of nonlinear polarization by simulation to describe the temporal variation of two-level system. Methods/statistical analysis: Software program was prepared in the study to solve normalized optical Bloch equation model numerically by Rung-Kutta-Fehelberg method. Findings: The study showed that the dispersion not occurs at resonance state, while occurs at detuning state, it decreases with the increasing of detuning, so the decreasing of absorption, population inversion was observed with the increasing of detuning. While the value of saturation parameter increases with the increasing of detuning value. Application/improvements: The appropriate intensity (saturation intensity I sut.) to reach the steady state of population inversion as a function of initial (incident I int.) intensity on the system has been estimated.