Based on the Lband secondbysecond radiosonde data, a second by second quality control method is developed. A series of quality control measures were devised to deal with various issues after observation, such checks as on large segment data missing, instantaneous value, cast point, balloon cast time, height difference, temperature variability, air pressure variability, relative humidity variability, elevation angle variability, horizontal angle variability check, slant range variability, rising speed, end point, and constant value. According to the quality control results of the second by second radiosonde data over Sichuan in 2016, the quality control method performed well. The quality control results show that the number of observations passing the height difference check is only 1105 The number of observations passing the slant range variability check is 2221 The passing rate of horizontal angle variability check, temperature variability check, and elevation angle variability check are 60% to 70%. The passing rates of cast point check, balloon cast time check, relative humidity variability check are close to 90%. The passing rates of other checks are more than 90%. Generally, in the second by second radiosonde data, the frequency of abnormal slant range data is relatively higher, and the cases in excess of the threshold of the height difference calculated by radar and the pressureheight formula are more frequent. The suspicious messages by other checks are less.