The cigar-filler tobacco variety Chuxue 14 （CX-14） was used to optimize the application amount of magnesium fertilizer for tobacco leaves.A field experiment was conducted to study the effects of the application amount of magnesium fertilizer on the growth，yield，quality，and flammability of cigar-filler tobacco leaves.5 treatments including the application amount of magnesium fertilizer of 0 （CK），60，120，180，and 240 kg/hm² （calculated as MgO） were set up.The results showed that the yield，economic value，and the proportion of high-grade leaves in cigar increased initially and then decreased with the increase of the application amount of magnesium fertilizer.Compared with CK，the application amount of magnesium fertilizer 60-180 kg/hm² to CX-14 reduced the content of nicotine，ignition temperature and the rate of total weight loss of tobacco leaves，while increased the maximum rate of heat flux and total heat release，reduced the activation energy and increased the frequency factor.When the application amount of magnesium fertilizer was 120 kg/hm²，the yield and economic value of cigar-filler tobacco reached the highest level.Compared with CK，the content of ash decreased by 24.5%，while the ignition temperature and activation energy decreased by 11.0% and 4.8%，respectively.The rate of total weight loss，maximum rate of heat flux and total heat release，and frequency factor increased by 5.7%，15.6%，6.0%，and 21.6%，respectively.The ignition index （D_i），flammability stability index （F_i），and comprehensive flammability index （I_CC） was the highest as well，with the best overall performance of flammability.It is indicated that the application amount of magnesium fertilizer of 60-120 kg/hm² can increase the yield and economic value of tobacco leaves and the proportion of high- grade tobacco，improve the flammability of tobacco leaves.The comprehensive flammability of tobacco leaves is best when the application amount of magnesium fertilizer is 120 kg/hm².