There occur frequently observation data errors induced by various causes, such as observation instrument breakdowns resulted from thunders and lightning, electromagnetism interruption from AMS sensor calibration and replacement, data missing from degraded sensor capability, etc. In order to ensure the complete and continuous records，based on twoyears experiences of data checking at the Jiaxing station， Aformat and Jformat data missing， wild values， errors in format, etc., are discussed, aiming to reduce the frequency of mistakes in data checking and to improve the data quality.