We report here an efficient, high power, narrow linewidth 1.9 μm gas Raman amplifier by means of a hydrogen-filled hollow-core fiber. A 1.9 μm narrow linewidth continuous wave seed laser is coupled into the hollow-core fiber together with a high power pulsed 1064 nm MOPA laser through a shortpass dichroic mirror, and then amplified by stimulated Raman scattering of hydrogen. With 2 m fiber length and 4.5 bar gas pressure, the maximum average 1908 nm Stokes power of 570 mW is obtained, a record average power level for such experiments. The maximum peak power is about 50 kW, the linewidth is about 1 GHz, and the quantum efficiency is about 51%. This work has demonstrated the potential to get a high average power gas Raman laser in a hollow-core fiber, and it further provides the possibility to achieve a high average power 4 μm midinfrared fiber laser by cascaded gas stimulated Raman scattering.