Abstract: In order to clarify the effect of air-drying density on non-volatile organic acid metabolism of cigar tobacco leaves, taking Dexue No.1 as the test material, the effects of three treatments (stick distance of 15, 25 and 35 cm) on the temperature and humidity of the drying room, tobacco leaf moisture content, the chemical composition, the content of non-volatile organic acids, and the malate dehydrogenase (MDH), succinate dehydrogenase (SDH) and citrate synthase (CS) activities were studied. The results showed that with the progression of air-curing, the moisture content and malic acid content showed a downward trend, the citric acid and malonic acid contents showed an upward trend, and the overall change of the oxalic acid content was not significant. The activity of MDH increased first and then decreased, CS activity increased all the time, while SDH activity gradually decreased. Under the drying density of 25 cm, the temperature and humidity in the drying room were suitable, which can increase the MDH, SDH and CS activities and the contents of citric acid and oxalic acid, reduce the contents of malic acid and malonic acid of tobacco leaves, and the chemical components were coordinated. Therefore, the air-curing density with a length of 25 cm can improve the metabolism of non-volatile organic acids, promote the conversion of internal materials, and improve the quality of tobacco leaves.