We used 208 of flue-cured tobacco leaf samples from Southwest China in 2002-2005 to study the distribution of pH in flue-cured tobacco leaves among different leaf positions, harvest years and tobacco growth regions, and analyze the relationship by regression between pH and sensory quality. The results showed that leaf pH in southwest China ranged between 4.6 and 5.2, with the mean of 4.90, standard deviation of 0.16 and variation coefficient of 3.35%. The leaf pH had significant difference among different leaf positions, harvest years and tobacco growth regions. When pH changed from 4.5 to 5.5, there were significant regression relationships between pH and quality of aroma, after taste, offensive taste, biting taste, combustibility as well as total score, but the regression relationships between pH and volume of aroma, strength, density as well as ash were not significant at 5% level.