In order to clarify the effects of tillage patterns on farmland weed community structure and crop production characteristics, based on 10 years location experiment with notillage, subsoiling and conventional tillage in the cold and arid region of North China, and supplementary experiment of plowing after 10 years notillage and subsoiling, oat was planted in 2 soils under different tillage patterns, and field weed total density, dominant weed types, weed diversity index, field weed biomass and oats yield were measured. The results showed that the regional weed community was dominated by foxtail weed (Setaira viridis); the weed density under longterm notillage was 2.20-5.14 times of tillage at different growing stages of oat, but there were no significant differences between conditional tillage and plowing after longterm notillage and subsoiling. Field weed Shannon diversity indices were 0.429 and 0.531, respectively, for sandy chestnut soil and loamy meadow soil under notillage conditions, and field weed biomass values were 1.35 and 2.26 times of plowing treatment, while the oat biomass values were only 2807.4 kg·hm^-2 and 4053.9 kg·hm^-2, decreased by 22.3% and 46.2%, respectively. The results showed that the weed community characteristics were affected by both tillage patterns and soil types. Longterm notillage farmland in the cold and arid region of North China could promote the natural evolution of plant communities by keeping more perennial weeds, and the plowing pattern lowered the annual weed density, eliminated perennial weeds with shallow roots, and stimulated perennial weeds with deep roots.