A high-power and narrow-linewidth MgO-doped periodically poled LiNbO3 optical parametric oscillator was reported, which is based on a volume Bragg grating output coupler pumped by a linearly polarized Q-switched Nd: YAG laser. Maximum output power of 8.4W at a wavelength of 2.1μm with beam quality factor M2 of 3.8 and 4.1 in horizontal and vertical directions was obtained using a double-pass pump four-mirror standing-wave geometry. The spectral bandwidths are 0.41nm and 0.53nm for signal and idler waves, respectively, which are confined within 2nm.