Abstract: In order to improve the accuracy of on-line NIR for determination of routine chemical components in cut tobacco in primary processing,NIR spectra of tobacco samples were collected at different moisture contents,temperatures and measuring optical paths in a laboratory where the test conditions were analogous to the online conditions.By mathematical models,the nicotine and total sugar values of tobacco samples were predicted and compared with the determined values.The results showed that:1) within the experimental range,the relative error of on-line NIR measuring results increased with the rising of moisture content and temperature of tobacco sample and the decrease of measuring optical path;2) the optimal on-line NIR detection conditions for cut tobacco samples were:moisture content from 12% to 13%,temperature from 25 to 30℃ and measuring optical path from 16 to 20 cm.