A high energy femtosecond fiber laser based on Yb-doped single polarization large-mode-area photonic crystal fiber is demonstrated. A simple linear laser cavity is used. The laser works in soliton mode-locking regime due to the negative dispersion generated by a pair of gratings implemented in the cavity, while the self-starting mode-locking operation is achieved by sermiconductor saturable absorber mirror. The fiber laser directly generates 518 fs laser pulses with the average power of 700 mW at the repetition rate of 47.3MHz (corresponding to a pulse energy of 14.8 nJ). The single pulse energy is two orders higher than that of conventional soliton mode-locking fiber laser.