Liaoning and Jiangsu are main regions seriously infested by weedy rice (Oryza sativa f. spontanea ) in China. Weedy rice samples collected from 29 sites in 14 cities of the two provinces were cultivated in Nanjing, and 23 traits during vegetative and reproductive growth stage were observed and measured in order to reveal the diversity and identification traits of weedy rice. The results showed that there were differences of traits in terms of plant height after one month, tiller number after one month or two months during vegetative stage, and in terms of pericarp color, grain length/width ratio, 100-seed weight, shattering habit, culm rigidity, flag leaf width, flag leaf length, yellow maturity, half-yellow maturity–half-heading, full yel-low maturity during reproductive stage between weedy rice and cultivated rice in the two provinces. The scatter plot of the first and second principlal components (their cumulative contribution accounting for 43.24%) also showed that there were differences between Liaoning and Jiangsu weedy rice, as well as be-tween weedy and cultivated rice of the two provinces. Cluster analysis based on Euclidean distance showed that weedy rice populations could be divided into two types: Japonica-like and Indica-like weedy rice. Liaoning weedy rice populations fall into first category. Jiangsu weedy rice populations fall into both catego-ries. Weedy rice of the two provinces can be further divided into 6 classes: (I) the Japonica-like type with strong shattering, light grain weight, short stem and prematurity; (II) the Japonica-like type with no awn, many panicle, late maturity, narrow flag leave and strong dormancy; (III) the Japonica-like type with long awn, weak tillering, few pancle and weak shattering; (IV) the Indica-like type with hard culm, wide flag leave, late maturity and strong dormancy; (V) the Indica-like type with red pericarp, long grain, soft culm, and heavy grain weight; (VI) the Indica-like type with no awn, tall stem, long flag leave and long panicle. The study on the morphological index and classification of weedy rice in the two provinces may provide theoretical basis for prevention and control of weedy rice.