The interactions between a chirped ultra-short pulse and two-level medium on near-resonant were investigated. According to the semi-classical theory of light-matter interaction, the modified Bloch equations with chirped terms were established, and an accurate and efficient fourth-order Runge-Kutta method were applied for solving the equations. After numerical simulation, the relationships between the sign (and value) of chirp and Bloch vectors were obtained, and the influences of signs of detuning and chirp on Bloch vectors were also gained. The numerical results show that, the sign and value of chirp have obvious modulation effects on the transient coherence and steady-state of Bloch vectors, which provides us to control the two-level system by adjusting the pulse chirp.