The relationships between major climatic factors in different growth periods of Liangshan tobacco-growing areas and chemical compositions of tobacco were investigated by using simple correlation and canonical correlation analysis. The result indicated that the effect of climatic factors on leaf chemical composition, from high to low were as follow: daily average temperature ＞relative air humidity＞sunshine hours＞precipitation＞daily range of temperature. During field growth phase, the weather in the fast-growing stage had the greatest impact on the chemical composition. Meteorological factors were most influential on the reducing sugar, total sugar, total alkaloids and potassium content of flue-cured tobacco leaves. The contents of leaf total sugar, reducing sugar and total alkaloids showed a positive correlation with temperature of the root extending stage, maturity temperature, and maturity relative air humidity, and showed a negative correlation with temperature and relative air humidity of the fast-growing stage. Sugar and alkali showed a positive correlation with maturity rain fall. Within certain range, fast-growing stage temperature and relative air humidity reduction, as well as the increase of fast-growing stage sunshine hours and maturity rainfall was obviously in favor of the increase of leaf potassium.