Abstract: To study the species, distribution and damage of weed in tobacco fields in Sichuan Province, an inverted "W" 9-point sampling method was used to investigate the weeds in 289 tobacco fields in Sichuan. The results showed that there were 201 weed species belonging to 135 genera of 41 families. Digitaria sanguinalis (L.) Scop., Polygonum nepalense Meisn., Alternanthera philoxeroides (Mart.) Griseb, Echinochloa colonum (L.) Link and Galinsoga parviflora Cav. were the dominant weeds. Commelina communis L., Chenopodium serotinum L., Paspalum distichum L., Polygonum lapathifolium L. var. salicifolium Sibth, Kalimeris indica (L.) Sch.-Bip. and Avena fatua L. were regional malignant weeds. Common weeds and general weeds included 24 and 166 species, respectively. The species diversity, Gleason index and Shannon-Wiener index of weeds were the highest in tobacco fields in Yibin and Dazhou, and the distribution of species was relatively even. Gleason index, Shannon-Wiener index and Pielou index of weeds were the lowest, while Simpson index was the highest in tobacco fields in Liangshan and Panzhihua, and dominant species were outstanding. The results of cluster analysis indicated that the weed communities could be grouped into 3 categories according to regions:Yibin-Luzhou-Guangyuan-Dazhou, Liangshan-Panzhihua and Deyang. The differences of geography, climate and weed control measures may be the main reasons causing the differences in weed community structure in tobacco fields.