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The thesis surveyed weed species and community structures of linseed fields in the main producing cities of Wuwei,Baiying, Lanzhou, Dingxi, Pingliang and Qingyang in GANSU Province The results showed that there were over 200 species of weeds in the linsccd fields in GANSU Province, the dominant populations in the weed communities were Polygonum convolvulus,P.sibiricum, P.aviculare, Chenopodium album, C.serotinum, C.glaucm, C.aristatum, C.foetidum, Kochia scoparia, Salsola collina, Suaeda glauca, Amaranthus retroflexus, A.lividus, Stellaria media, Lepyrodiclis holosteoides, Hypecoum leptocarpum,Capsella bursa-pastoris, Chorispora tenella, Descurainia sophia, Lepidium apetalum, Malcolmia africana, Vicia bungei, Medicago sativa, Erodium stephanianum, Hibiscus trionum, Calystegia hederacea, C.sepium, Lappula echinata, Lycopsis orientalis, Elsholtzia ciliate, Solanum nigrum, Plantago asiatica, Galium aparine var.tenerum, Cephalanoplos segetum, C.setosum, Ixeris chinensis,Lactuca tatarica, Sonchus brachyotus, S.oleraceus, Taraxacum mongolicum, Xanthium sibiricum, Avena fatua, Setaria viridis,Echinochloa crusgalli var.mitis, Leymus secalinus, Phragmites communis, Poa annua, Chloris virgata and Digitaria sanguinalis,etc.The weeds was divided into39 community groups, there were 8 main community groups.