The precision measurement of the temperature field is of great significance in many fields, such as machinery, aerospace, biomedicine, food and chemical engineering, electric power, energy, and environment. A three-dimensional temperature field measurement method based on multi-step phase shift method and polarization interference optical tomography optical path is proposed. First, the polarization interference optical tomography measurement system is designed by combining the Mach-Zehnder interference optical path structure and optical tomography technology, and the multi-step phase shift is realized by using the rotation of the polarization device to achieve high-precision signal detection. Then, the three-dimensional refractive index distribution of the measured medium is restored by the exponential filtering backprojection algorithm, and the three-dimensional temperature field distribution is obtained. Finally, the measurement formulae are derived and the experimental system is built. The error analysis shows that the system measurement uncertainty is about 0.8 ℃ under the existing experimental conditions. The measurement experiment and comparison results show that the measured temperature field is consistent with the actual situation, and the result is less than 2 ℃ compared with the calibration temperature of the platinum resistance thermometer.