The precision temperature control method of the optical frequency discriminator and its influence on optical transmission spectrum and measurement error are studied. A double-deck temperature controlling structure and corresponding circuit are designed, and the influence of the wire resistance is reduced by using a three-wire equal length method and dual switchable current source, and the mismatch of the current source is eliminated. The analog and digital hybrid temperature control method based on field-programmable gate array (FPGA) is studied. Control experiment with different temperature set points show that the temperature control accuracy is 0.0062 ℃ and the temperature measurement error is 0.0036 ℃. The influence of the temperature control accuracy on the spectral line movement and transmittance of the optical frequency discriminator is tested with a single-frequency ultraviolet laser. The transmittance spectrum line translation under this temperature control accuracy is 0.11 MHz, resulting in a speed measurement error of 0.0195 m/s.