This paper introduces a 2.7 μm acousto-optic Q-switched device with high damage threshold. With comparison and analysis of several commonly used near-infrared acousto-optic materials, the lithium niobate crystal is a preferred medium material for the Q-switched device, which can provide suitable compromise among diffraction efficiency, optical performance, and resistance to laser damage. This paper also analyzes the relationship between Q value of the laser cavity and the diffraction efficiency. The purpose of reducing the driving power and improving the turn-off capability is achieved by optimizing the distribution of diffraction efficiency. This 2.7 μm acousto-optic Q-switched device made of lithium niobate crystal has an operating wavelength from 2.7 μm to 2.8 μm, an operating frequency of 40.68 MHz, an optical aperture of 3 mm, and a diffraction efficiency of 75% at the center part of the through hole. Compared with the acousto-optic Q-switched device made of tellurium oxide, the 2.7 μm acousto-optic Q-switched device made of lithium niobate crystal has higher laser damage resistance.