Abstract: In order to find the optimal environmental temperature and relative humidity (RH) during cigarette making, the relationships of the change rate of long strands proportion, individual cigarette weight, and ratio of loose-end cigarettes with environmental temperature and relative humidity were studied for flue-cured type cigarettes of different classes. The results showed that the cigarettes of Class A, B and C made under 24℃ and RH57%, 25.5℃ and RH60%, and 26.5℃ and RH62%, respectively, possessed the lowest individual weight and loose-end ratio. It is appropriate to set ambient temperature and relative humidity in cigarette making workshop according to the class of the cigarettes being made, possibly, to make cigarettes of different classes in different zones or different periods of time separately where necessary for pursuing better cigarette quality.