The dependence of self-mode-locked Ti:S laser pulses on the intracavity net negative group-delay-dispersion is investigated in detail in this work. The results show that the central wavelength spectrum, bandwidth and duration of laser pulses will change with the movement of intracavity prisms. The multi-peak structure of spectra is observed and explained theoretically. Also, a formula of pulse duration is pointed out in this paper. The shortest pulse width up to 14.6 fs is generated in our laser.