A swept-source laser by using an Acousto-optic Tunable Filter(AOTF) was researched to improve the stability of the source output. The principles and method to implement output stability of the source were described, and corresponding parameters of the source were analyzed. An acousto-optic tuning was selected to replace the mechanical filtering to improve its output stability. A Semiconductor Optical Amplifier(SOA) was used as a gain medium and the AOTF was used as a wavelength-selected element in an internal fiber ring cavity. The acousto-optic interaction was used in the filtering of light in the cavity. With the SOA injection current of 280 mA, the continuous wavelength tuning range of the source is from 1 294 to 1 368 nm centered at a wavelength of 1 330 nm, and its sweep rate is 3 731 Hz, the full width at half maximum is 51 nm and the output power from the ring cavity is 1.14 mW. By using the electric control element AOTF, the system implements the electronic tuning without mechanical movement elements, so it shows good output stability and excellent spectral repetition. It concludes that the swept-source laser obtained by this method has a stable output and satisfies the requirements of the other parameters of the swept source optical coherence tomography.