This article analyzes the problem of outoftolerance error in the field calibration of the new type evaporation measurement system in terms of AWSs. The root cause of the outoftolerance error is that the measurement system shows no negative value for the baseline value (zero value), and the design of the communication unit introduces the water level compensation. In order to control the reliability and validity of the field calibration evaporation data within the allowable range, the calibration data are processed by a correction method (the base point of 10 mm and the reciprocal of the sensitivity coefficient of 981% are reselected). The test proved that the qualified rate of the new evaporation calibration is greatly improved. The results show that the correction method solves the problem of outoftolerance error of evaporation field calibration and makes the calibration data of evaporation more accurate and reliable. Therefore, it is suitable for the data processing of the new type evaporation measurement system in the field calibration.