Abstract: In order to determine the best muscle-yellowing temperature for flue-cured tobacco variety NC55, three muscle-yellowing temperatures (45, 47 and 49 ℃) were tested. The physiological and biochemical changes of each treatment such as water, pigment, amylase, polyphenol oxidase during bulk curing, appearance quality of cured tobacco leaves were analyzed and compared. The results showed that 47 ℃ muscle-yellowing temperature treatment had stable amylase activity, fully starch degradation, low polyphenol oxidase activity, low starch content in cured tobacco leaves, high total sugar and reducing sugar contents, orange tobacco, average price, high-middle-quality ratio, high neutral aroma components. Water-loss rate under 49℃ muscle-yellowing temperature treatment was obviously faster than 45 ℃, 47℃ treatments, thus affecting the formation of neutral aroma components to some extent. Polyphenol oxidase activity under 45 ℃ muscle-yellowing temperature treatment was higher than those of 47 ℃ and 49 ℃ treatments, resulting in more variegated leaves. Considering appearance quality and inner chemical quality, 47 ℃ muscle-yellowing temperature treatment is beneficial to producing more aromatic matter and improving the quality, is more suitable for flue-cured tobacco NC55.