The wet bulb temperature is an important meteorological parameter in heating, ventilation, power plant cooling towers and other many engineering designs. As automatic weather stations (AWS) are widely used in the meteorological station, the direct observation data of wetbulb temperature gradually stop, which gives difficulty in the engineering design parameters of wetbulb temperature in the weather analysis and the application. For the calculation of the wetbulb temperature at AWS, we employed the groundbased meteorological observation humidity formula and the basic idea of Newton’s iterative method, and obtained a simplified general iterative formula. An empirical formula of wetbulb temperature is used to calculate its initial value, and an EXECL spreadsheet is used to complete the iterative calculation of wetbulb temperature. The results show that, this calculation method of wetbulb temperature has high accuracy, less computation, as well as the calculation process simple and controllable. Therefore, it can be widely used in the wetbulb temperature calculation at AWS.