A L-band high power sub-picosecond erbium-doped fiber laser is reported. Two polarization controllers (PC) and a polarization dependent optical isolator (ISO) are fused in all fiber ring cavity, and the mode-locked laser pulse output of all fiber structure is realized based on nonlinear polarization rotation mode locking principle. The center wavelength of the laser is 1603 nm, the pulse repetition rate is 37.8 MHz, the single pulse energy is 4 nJ, and the average output laser power is 152 mW. Reasonable dispersion management is carried out on the all fiber mode-locked laser, and the mode-locked laser output with pulse width of 370 fs can be obtained. The erbium-doped fiber with high doping concentration is adopted in experiment, and its length is reduced effectively. The pump conversion efficiency is improved. The L-band sub-picosecond fiber laser with simple and compact structure, stable and reliable performance is realized.