Abstract: The design and simulation of an all-fiber ytterbium doped passively mode-locked fiber laser were presented which generated ultrashort pulses as the laser seed. The passive mode -locking was achieved by using the nonlinear polarization technology, and the normal dispersion was compensated by the all solid photonic bandgap fiber. As a result of the simulation and optimization, the ytterbium doped fiber laser generated the 0.7 ps pulses with 0.89 nJ energy. The simulation results suggest that the passive mode -locking method and the dispersion compensation method are useful for achieving the ultrashort pulses which meet the requirements to be the laser seed.