Abstract: In order to study formation fluids in the high-wax condensate gas reservoirs in Dalaoba gas field, experiments and tests are carried out for wax appearance temperature（WAT）and on-line wax precipitation amount of condensate oil with a laser test device and in-line filters connected to high-temperature and high-pressure DBR-PVT tester. Meanwhile, gas is injected to test WAT after multiple backward contacts. The paper compares the results with those obtained from the theoretical calculation model for paraffin deposition. The analysis shows that if paraffin components are considered as adjustable parameters, the modeling results of WAT and wax precipitation amount could match with the experimental results very well. If the mole fractions of paraffin components are put into the theoretical model, WAT and wax precipitation amount before and after multiple backward contacts could be well predicted. Using this fluid system to perform modeling and calculation, the changes of fluid compositions with different contact frequencies and wax precipitation amount at different temperatures can be obtained after gas injection in Well DL4. The injected gas mainly plays the role of extraction, which will result in the increase of heavy component content in the fluid and the rise of WAT. The results can provide basis for calculation of wax precipitation amount before and after gas injection in condensate gas reservoirs