Abstract: The composition and econiches of weeds in wheat fields of the Yellow River irrigation zone of Lanzhou were field investigated based on eco-niche theory and method. The results show that Calystegia hederacea, Chenopodium album, Cephalanoplos segetum, Portulaca oleracea, Amaranthus retroflexus, Setaria viridis, Sonchus brachyotus and Polygonum aviculare form the main eco-damage population. Based on calculations of time, horizontal and vertical stretches of weed eco-niches, C. album is the dominant species and C. hederacea is the main weed. C.album and C. hederacea niches extensively overlap. The result illustrates that potential factors of wheat field weeds will induce field weed communities change as field environment varying.