In order to make the field calibration specifications for AWS evaporation sensors suitable for the actual work better, according to the characteristics of ultrasonic evaporation sensors, work experiences from field calibration, and some experimental data, some problems existed in calibration procedures of AWS evaporation sensors are discovered and analyzed, and some suggestions are proposed, such as making repeatable measurements, changing maximum permissible error to ± (01 mm+15% H), and describing the calibration method clearly in use of the whole standard modules, so to improve the field calibration indexes and methods of ultrasonic evaporation sensors. It provides references for the preparation of new calibration specifications.