In this study, a high-efficiency fiber gas laser source is developed in a single-pass deuterium-filled hollow-core photonic crystal fiber by rotational stimulated Raman scattering (SRS). The ordinary dominant vibrational SRS with relatively large gain is suppressed because of the special transmission properties of this low-loss hollow-core photonic crystal fiber, permitting its efficient conversion to a rotational Stokes wave. A homemade 1540-nm nanosecond pulsed fiber amplifier is used to pump a hollow-core photonic crystal fiber having a length of 20 m with a high-pressure deuterium gas. Thus, a high-efficiency 1645-nm Raman laser is obtained using a single-pass configuration. A maximum average output power of ~0.8 W (single-pulse energy of ~1.6 μJ) can be obtained with respect to the 1645-nm Raman laser at a pressure of 2 MPa, and the slope efficiency is observed to be ~71.4%. This study introduces a simple and effective way for the realization of 1.7-μm-band fiber lasers.