In order to control weeds safely and efficiently, the quadrat survey procedure was used to investigate weed species and their distribution in oats fields in Wuchuan County of The Inner Mongolia Autonomous Region. The results showed that there were 27 species belonging to 22 genera of 13 families. Of all species recorded, broadleaved weeds (21 species) accounted for 74.29%, the grass family (2 species) for 14.29%. The main weeds were Setaria viridis (L.) Beauv., Chenopodium a1bum Linn., Agriophyllum squarrosum (L.) Moq., Salsola collina Pall., Herba Sonchi Brachyoti. The weed species in the no-tillage field were more than that in conventional tillage filed. The weeds in the no-tillage with out mulch field were serious, but the weeds in the no-tillage mulch field were fewer.