In this study, precise visualization method for temperature field of a natural convection cell is developed by phase-shifting interferometry in this study. To precisely obtain high-resolution local temperature information from observed temperature field, a phase-shifting interferometer is utilized in the present system. The target cell is arranged with internal natural convection flow of distilled water (Pr = 5.9). The experiments are conducted under low and moderate Rayleigh numbers (Ra ≤ 8.87×10⁴) with specially designed test cell. High phase-resolution data has been achieved by using phase-shifting image processing technique developed in this study. In detail, two-phase unwrapping technique, which can effectively filter out the measurement noise, is capable of unwrapping the phase data for the temperature field. To make a validity of present visualization method, a three-dimensional numerical simulation was performed under the same boundary conditions with the experiment. 3D temperature field of numerical simulation is integrated along optical path direction to 2D image and compared with experimental results. It is found that: (1) the experimental results and numerical analysis show good agreement; (2) the visualization method is reliable and accurate for measuring temperature distribution of natural convection. Future studies should focus on the boundary conditions effects, so as to provide an in-depth understanding of thermally-driven natural convection through the new measurement technique developed in this study.