Abstract: A new SBS model, which is described as self stokes seeding (SSS), is brought forward and its mechanism is researched. The SBS coupled wave equations are solved numerically and laser induced stress is obtained spatially. Theoretical model is established to study the damage process inuced by SSS process and damage thresholds are calculated. Physical chracteristics which should be embodied by SBS damage mechanism are analyzed, and the dependence of laser pulse width and interaction length on damage thresholds is presented. The theoretical research shows that the SBS induced damage mostly happens at the entrance surface of pump laser and the threshold intensity is inversely proportional to laser pulse width and the interaction length.