Abstract: To find the difference in various evaluation standards and obtain optimal calculation and evaluation results, calculation formulas and evaluation methods in different standards for performance tests of cooling towers were analyzed by examples. Results show that different standards have different calculation and evaluation methods, which have a great impact on the final result and evaluation conclusion, including the methods for calculating the coefficient of heat carried by evaporation, the heat balance error, the air density, the air enthalpy, the saturated steam pressure and the number of transfer units, as well as the difference in curve fitting and reading. By referring to appropriate calculation formulas and evaluation methods in various standards, the accuracy of corresponding test results can be improved.