The design and application of an all-fiber coupled single polarization acousto-optic modulator is introduced in this paper. The working principle of the fiber acousto-optic modulatoris analyzed theoretically, and the design methods of the key indicators including insertion loss, extinction ratio, rise time of light pulse and the coupling process method of single polarization fiber collimatorsare presented. A single polarization fiber acousto-optic modulatorworking at a wavelength of 1.06 μm with high speed and low insertion loss is designed and manufactured. The polarization extinction ratio (PER) reaches 42 dB, which effectively isolates the polarization noise of the system.