Abstract: PVT experiment is a conventional method used to determine the phase characteristics of oil and gas at different pressures and temperatures, which helps oil exploration and development workers to more accurately and quickly determine the physical parameters of oil and gas. At present, there are still two unresolved problems in the PVT experiment of condensate gas. One is that a check is carried out only on the monotonicity and ranges of similar experimental data, and there is a lack of a checking method suitable for different PVT experiment data. The other is that the volume factor of condensate oil and dissolved gas-oil ratio cannot be directly measured by experiments, while the phase simulation software adopts the method of fitting before calculation, and many uncertainties still exist. In view of above problems, based on the principle of phase separation volume equilibrium under standard conditions, in combination with equal composition expansion and equal volume depletion experiment conditions, the paper establishes the material balance equation and material balance equation for both equal composition expansion experiment and equal volume depletion experiment on condensate gas, respectively. Compared with the commercial phase state simulation software, for the condensate gas with high condensate oil content, the relative errors of relevant parameters under different depletion pressures calculated by the laboratory material balance equation are as follows:1.9 % for retrograde condensate saturation, 2.8 % for condensate volume coefficient, and 6.3 % for the solution gas-oil ratio in condensate oil, indicating that the both are in good agreement with each other. Three application examples demonstrating that the laboratory material balance equation plays an important part in the basic research on condensate gas reservoir development are listed as below:(1)Based on the routine checking of similar experimental data, the matched checking process for different experimental data can be further achieved. (2)Without adding any new experimental equipment and experimental procedures, the condensate oil volume coefficients and solution gas-oil ratios can be simply calculated while checking the quality of experimental data. (3)Considering the influence of the pressure stages of equal volume depletion experiments, dynamic indicators for the natural depletion of constant-volume condensate gas reservoirs can be predicted.