This experiment was carries out to study on the effect of temperature raising rate to chemical composition of tobacco leaves during the midrib drying stage of flue-curing. The results were as follows : In the case of the temperature raising rate became more rapidly during midrib drying stage. It had a tendency to increase in oxailic acid, succinlc acid, ammonia, polyphenol; there was a large loss of total sugar, reducing sugar, malic acid, palmitic acid and linolenic acid; leaf color became more reddish; the leaf quality index value decreased, thereby the quality of external appearance deteriorated. It is desirable that the temperature raising rate had to be more slowly.