Abstract: Yunnan Province has a complicated geographical environment, in which altitude differences are larger from place to place and regional climate differences are significant. But the province has the largest tobacco leaves output in China, with its flue-cured tobacco growing areas being distributed in the altitude interval of 1000-2000 meters. In order to understand the internal relations between chemical quality of flue-cured tobacco and planting climate, based on the field experiments and related climate data in 10 counties(districts) from 2017 to 2020 in Yunnan, the methods of systematic clustering and principal component analysis are used to analyze the effects of planting climate on the contents of nicotine, total nitrogen and protein inside local tobacco leaves. The results showed that the climate of tobacco-growing areas of Yunnan province in tobacco field growth period (from mid-April to late August) was divided into six types, which meant Yunnan had the climate diversity of flue-cured tobacco planting. But most of the planting climate types had the main climatic characteristics of the low latitude plateau region of Yunnan in summer half year, which manifested that lower average air temperature appeared in flue-cured tobacco field growth period with the average values being lower than 22.5℃ in hottest month. Simultaneously, there were higher average relative humidity (being higher than 80%), more rainfall (being greater than 5.5mm per day on average) and lesser sunshine duration (being less than 5.0 hours per day on average) in vigorous growth and mature period (mainly from June to August) of flue-cured tobacco, while there were lower average relative humidity (being less than 68%), rare rainfall (being less than 2.0mm per day on average) and more sunshine duration (being more than 7.0 hours per day) in transplanting and root growth period (from mid-April to mid-May). That is to say, in most tobacco-growing areas of Yunnan, the characteristics of the phased climate changes during the growing season were similar. Higher relative humidity and more rainfall in tobacco field growth period (especially in the mature period of tobacco from July to August) were conducive to increasing the contents of total nitrogen and protein inside tobacco leaves. And lower temperature conditions in field growth period (particularly in vigorous growth and mature period) were infavor of the accumulation of nicotine inside tobacco leaves. Meanwhile, the lower temperature conditions (including mean air temperature and shallow subsurface temperature) during the vigorous growth period (from late May to late June) of flue-cured tobacco would increase the contents of total nitrogen and protein inside tobacco leaves. The above-mentioned main climatic characteristics in Yunnan low latitude plateau during tobacco field growth season resulted in weakening transpiration and photosynthesis, improving temperature effectiveness for tobacco growth and prolonging growth and development period of flue-cured tobacco, which were the main reasons for the relative higher contents of aforementioned three chemical compositions inside tobacco leaves in Yunnan. The conclusion of planting climate effects on the chemical quality of flue-cured tobacco leaves was validated by related data from several provinces which produce flue-cured tobacco leaves in large amounts in China. The analyzed results could be applied to the development of characteristic tobacco leaves according to different local climatic conditions. They also would help to predict/evaluate the changes of chemical quality for tobacco leaves with climate conditions, and to provide scientific basis for tobacco industry to rationally deploy raw tobacco leaves from different places.