A watt-level Yb-doped ps fiber laser in tri-stage master oscillator power amplifier (MOPA) configuration is investigated. The first stage is a semiconduttor saturable absorption mirror (SESAM) passively mode locked fiber laser with a low average output power of 9.2 mW. A fiber Bragg grating (FBG) is utilized as the output laser cavity mirror. The second stage is an Yb-doped single mode fiber amplifier with a moderate average output power of 108 mW. The last stage is a double clad Yb-doped power amplifier which increases the average output power to 1.9 W. The center wavelength of the mode locked pulse is 1064 nm with a pulse width of 36 ps. The pulse repetition rate,the peak power and the energy of a single pulse is 29.6 MHz,1.8 kW and 61 nJ,respectively. A small dip located at the center laser wavelength is observed on the output spectrum,which is considered to be caused by the high reflectivity and the narrow bandwidth of the FBG.