Abstract: This paper mainly discusses the method of obtaining the wet ball temperature of automatic weather station by close query and iterative calculation. Based on the Gof-Gratch formula, a small humidity check scale with temperature at 0~48 ℃and intervals of 3 ℃ under unfrozen conditions is prepared. This check scale includes wet ball temperature t_w, vapor pressure e, relative humidity U, and pressure correction parameter n at each t value. The small humidity checklist can enable the calculation of t_w1 in batch using automatic weather station data such as t₁ and e₁. First, the t₁ and e₁ tables are linked to the small humidity checklist to make a close query. Secondly, an iterative calculation of t_w with a step length of ±0.1 is performed using t, e, and t_w values while keep e value unchanged. During this iteration, t changes with the value of t_w. Assume that the temperature of the changing wet ball is t'_w and the corresponding air temperature is t'. The t'_w is the solution of wet ball temperature t_w1 when |t'-t₁|reaches the minimum value. In order to improve the accuracy, t_w1 can be adjusted appropriately.