Abstract: The self-starting condition of the self-mode-locked Ti:Al2O3 laser suffered the influence of resonator parameters.Based on the analysis of the beam propagation in resonator,a self-mode-locked judgemental factor δ is obtained.A large δ corresponds the wide adjustment region of the mode locked area.In resonator,here are two areas satisfying both the self-mode-locked condition and self-starting condition.The self-mode-locked and self-starting region is a few tens μm.In experiment,the self-mode-locked and self-starting laser pulses of 74fs are obtained.The theoretical calculation is well agree with the experimental results.