Using the symmetrical split-step Fourior method, the evolution and linear chirp of the fundemental soliton under different gain parameters are numerically investigated in the erbium-doped fiber amplifier. The results show that when the gain parameter μ》1, the linear chirp can be generated after the fundemental soliton propagates along the fiber amplifier, and it’s found that the chirp characteristics are influenced by the fiber length. Meanwhile the part with linear chirp for the pulse is narrower if the chirp is more obvious. Moreover, further study found that the initial positive chirp parameter and the high soliton orders have an obvious and active effect on the linear chirp, which strengthens the pulse linear chirp. So the linear chirp can be generated by use of the nonlinear effects, when the fundemental soliton propagates along the erbium-doped fiber amplifier, which has an impact on pulse compression.