A 1.7- $\mu$ m pulsed laser is of tremendous interest for biomedical imaging applications due to its low scattering loss in bio-tissues, but is relatively difficult to generate in a fiber laser. In this paper, we propose and demonstrate a compact 1.7- $\mu$ m Tm/Ho-codoped fiber pulsed laser based on a novel intermode-beating modulation (IM) technique. A 1211-nm continuous-wave (CW) Raman fiber laser is especially homemade to pump a $\sim$ 20-cm short-length Tm/Ho fiber for obtaining $\sim$ 1.7- $\mu$ m optical gain. A pair of fiber end-facet mirrors with 1.7–1.8- $\mu$ m reflective band is used to form the all-fiber linear cavity. 1.76- or 1.78- $\mu$ m lasing is successfully achieved, and surprisingly exhibits stable self-gain-switching operation with $\sim$ 1- $\mu$ s pulse duration. Different from the conventional gain-switching requiring pulsed pumping, herein the gain modulation in the 1.7- $\mu$ m laser is induced by strong intermode-beating of the CW pump source. The pulse repetition rate with an increasing pump power is fixed at 145 kHz, which exactly coincides with the longitudinal-mode beat frequency of the 1211-nm pump laser. Our results may provide a new type of optical modulation (i.e., intermode-beating modulation technique) for a low-cost, compact pulsed laser.