Abstract: In order to control heat-forced maturity during flue-cured tobacco production in southern Hunan tobacco growing areas, the effects of major ecological factors on the heat-forced maturity were studied through field experiments to understand its formation mechanism. The results showed that the heat-forced maturity was caused by a set of comprehensive climatic factors. The rainfall amount in the early stage and the number of days with high temperature (daily maximum temperature ≥38 ℃) in the later growing stage significantly correlated with the heat-forced maturity rate, with the correlation coefficients of 0.904 and 0.914 respectively. Under the climatic conditions in southern Hunan, excessive rainfall in the early stage was the primary factor leading to the heat-forced maturity phenomenon, and excessive number of days with high temperature (daily maximum temperature ≥38 ℃) in the later stage was the major stress factor, while the excessive number of days with high light intensity (dailylight intensity ≥100 000 Lx)at the maturity stage was the secondary factor. The roots of flue-cured tobacco developed poorly due to excessive rainfall in their early growing, which reduced the plant stress resistance against high temperatures in the mature stage, thus leading to the phenomenon of heat-forced maturity.