A 1550 nm high efficient narrow line width fiber amplifier was demonstrated. In this amplifier double-stages amplification (MOPA) structure was employed. For the 1st stage(preamplifier), a piece of 5 m Er3+ doped fiber amplifier was used to amplifier the seed laser signal to about 90 mW. And for the second-stage amplifier, a piece of 15 m Er3+/Yb3+co-doped double-clad fiber amplifier which was pumped by two high power 980 nm LDs was employed to exhibit 1.97 W output with 10.8 W pump power. The conversion efficiency and slope efficiency reached 18 % and 21 % respectively, and a gain of more than 13 dB was obtained. In the experiment, a single frequency narrow line width(DFB)semiconductor laser with a pigtail was used as the seed source. The wavelength of the laser was 1.5 μm, and the output power may reached to about 10 mW. The line width of laser was measured by the delayed self-heterodyne method, The 3 dB line width of seed source and amplified laser was about 220 kHz. Under our current environment and conditions, the phenomenon that amplified laser line width was broadened was not found.