In terms of mass water content, field capacity, wilting moisture, and bulk density at 247 agricultural meteorological observing stations during 1981-2010 in China, effective quality control method of these data is applied according to climatic characteristics and soil texture as well as the theory of extreme values and relationship in soil hydrological constants. Analysis and calibration of singular historical observation data of manual soil water are conducted through each station and are presented in this paper taking typical stations as examples. As the base detective conditions, mass water content ranging in 0-50% and varying less than 30% during every two depths, field capacity ranging from 10% to 40% and varying less than 20%, wilting moisture ranging from 1% to 13% and varying less than 10%, bulk density ranging from 0.8 g·cm-3 to 2.0 g·cm-3 and varying less than 0.5 g·cm-3 are considered as credible data. Through typical analysis, errors of soil hydrological constants can be divided into three categories including the error of manual record, reduplicative observation and yearly obvious variation. Similarly, errors of mass water content exceedes proper ranges with minimum value of air dried soil moisture content and maximum one of saturated water content. One effective observation series of manual soil water can be obtained through quality control and applied for better understanding and scientific researches.