Abstract: In order to investigate the effect of self-pulsing of Yb3+ -doped fiber laser,the variation of photon density and inversed populations with pump power,the relationship among the damping coefficient,the output coupling reflectivity and doped particle concentration,and the variation of inherent oscillation frequency with output coupling reflectivity were simulated.The results show that the self-pulsing effect can be compressed with the decrease of the feedback of the output end and the increase of the doping concentration.Some measures to compress the self pulse of a fiber laser were put forward,providing a theoretical base for the design of Yb3+ -doped fiber lasers.