Objective To assess the diagnostic value of sweat conductivity testing in Chinese children with cystic fibrosis (CF). Methods This is a retrospective study. Sweat conductivity tests were conducted in 45 CF children (CF group) and 200 non‐CF children (non‐CF group) diagnosed with other chronic pulmonary diseases at the No. 2 Department of Respiratory Medicine, Beijing Children′s Hospital from May 2014 to June 2018. Pearson′s chi‐square test was used to assess the differences between CF and non‐CF groups. A receiver operating characteristic curve was constructed to calculate the best cut‐off value to diagnose or rule out CF. The pulmonary function parameters (forced expiratory volume in the first second, forced vital capacity,forced expiratory flows at 75% of exhaled vital capacity) of CF children over 6 years old were analyzed. The relationship between sweat conductivity and pulmonary function was compared between the two groups (80‐120mmol/L vs.>120mmol/L). Results The age of CF group was 9 (7, 12) years old, 19 males (42%) and 26 females(58%); the age of non‐CF group was 8 (5,11) years old, 106 males (53%) and 94 females(47%). The results of sweat conductivity test showed that sweat conductivity in CF group 108(99, 122) mmol/L was significantly higher than that in non‐CF group 43(36, 52) mmol/L (χ2=207, P<0.01). A cut‐off value of 80 mmol/L for CF diagnosis showed a sensitivity of 93.3% and a specificity of 98.5%. The receiver operating characteristic curve analysis suggested the best conductivity cut‐off value for the diagnosis of CF was at 83.5 mmol/L,with a sensitivity of 93.3% and a specificity of 100%,and an area under the curve of 0.993 (95% confidence interval 0.985-1.000). The best conductivity cut‐off value to rule out CF diagnosis was at 63.5 mmol/L,with a sensitivity of 97.8% and a specificity of 90.5%. There was no correlation between the level of sweat conductivity and the extent of pulmonary function decline. Conclusions Sweat conductivity testing can be used for the screening of CF in Chinese children. A diagnosis of CF should be considered if the value is greater than 80 mmol/L.