A quartz acoustooptic switch used for highpower laser is introduced in this paper. The acoustooptic switch uses quartz crystal as an acoustooptic medium, and lithium niobate crystal as transducer material. The working wavelength is 1 064 nm, working frequency is 68 MHz and diameter of the optical aperture is Symbol 4 mm. By optimizing the design of the acoustooptic interaction length, the firstorder optical diffraction efficiency can reach 95%. This paper also analyzed and measured the beam quality factor M2 of the diffracted light. By optimizing the crystal materials, improving the polishing quality, and rationally designing the heat dissipation structure, the diffraction light can preferably maintain the beam mode of the incident light.