Abstract: The temporal and spectral characteristic of two stacked chirped pulses are given based on the principle and model of the chirped pulse stacking. And the temporal modulation, spectral modulation and the nonlinear frequency chirp are analyzed. Some characteristics of the stacked pulse amplification are studied by evaluating the nonlinear Schrdinger equation. The amplification result changes with the modified chirped parameters, and the frequency chirp of the output pulse is also changed greatly. The result shows that self-phase modulation plays a main role in changing the spectral and frequency chirp of the amplified stacked pulse.