Phyto-sociological analysis of weed flora in Kharif and Rabi season of 2009-2010 conducted in Purulia, Bankura and Birbhum districts of West Bengal, India revealed that rice field was infested with 35 (8 grasses, 22 broad-leaved and 5 sedges), 24 (9 grasses, 10 broad-leaved and 5 sedges) and 45 (11 grasses, 28 broad-leaved and 6 sedges) weed species in Purulia, Bankura and Birbhum districts, respectively. In rapeseed-mustard 16 (4 grasses, 11 broad-leaved and 1 sedges), 9 (3 grasses, 5 broadleaved and 1 sedges) and 20 (3 grasses, 16 broadleaved and 1 sedge) weed species were observed in\ Purulia, Bankura and Birbhum districts, respectively. The wheat field of Purulia and Birbhum districts was infested with 12 (3 grasses, 8 broad-leaved and 1 sedges) and 20 (3 grasses, 14 broad-leaved and 3 sedges) weeds. A total of 13 (3 grasses, 9 broadleaved and 1 sedge) and 23 (4 grasses, 16 broadleaved and 3 sedges) weed species were observed in potato field of Bankura and Birbhum districts, respectively. Ludwigia parviflora recorded the highest values of frequency, dominance and importance value index in rice field of all the districts Whereas, the dominant weed species in rapeseedmustard, wheat and potato fields was Cynodon dactylon followed by Echinochloa colona and Digitaria sanguinalis among grasses, and Cyperus rotundus among sedges.