The present investigation was conducted to analyze the floristic composition of agro-ecosystem in Arar Northern Border region, KSA. A total of 30 sites were surveyed and a total of 42 taxa of weeds belonging to 21 families were recorded in agro-ecosystems in Arar. Poaceae was the most common family includes ten species, while both Asteraceae and Chenopodiaceae were characterized by four species each. The most abundant life form was therophyte represented by 30 species. From a phytogeographical point of view, Mediterranean taxa were represented by 14 species. Also, 14 species were belonging to cosmopolitan phytochoria. Several soil physical and chemical parameters were analyzed in the collected soil. Studied 30 stands were classified into two groups using TWINSPAN; negative group includes 16 stands characteristic with Lamium amplexicaule as indicator species, while the positive group includes 14 stands and the indicator species for this group are Trianthema portulacastrum, Sonchus oleraceus, Chenopodium murale, Bidens pilosa and Ricinus communis