In order to enhance the accuracy of the records observed by small evaporation pans, an analysis is made of the false evaporation records from January 1998 to December 2007, including negativevalue, greaterthannormal, and missing records, in combination with weather conditions. The results show that the negative occupies 54.8% in false records, mostly in November and next February, under the conditions of light rain (snow), continuous rain, and bad fog weather; greaterthannormal and missing records appear mostly in June, July, and August under the conditions of showery heavy rainfall, small humidity, strong sunshine, and high wind weather. The causes of false records include improper and unreasonable operations and special weather. Some suggestions to avoid false records are presented corresponding different weather conditions.