Abstract: A modulation function related to the total gain of amplifier chains was established to compensate the spectral gain narrowing in high-power ultrashort-pulse laser systems. The modulation function to be used for a system could be given by putting in all data of the system, including the spectrum of the total gain, bandwidths of the gain medium and laser pulse, and central wavelength. For different laser systems, the form of the modulation function could remain the same. Spectral compensation simulations for the SILEX-I Ti:sapphire laser system were conducted by modulating the seeding pulse with a designed function at different parameters of bandwidth of gain medium, laser spectral width and laser central wavelength etc. The simulation results indicate that this modulated function is very go