In the early 21st century, weedy rice occurred just in some regions of Jiangsu Province. But it has already been popular in the whole province by far, which caused serious damage to high and stable yield of japonica rice. In order to reveal the mechanism of rapid occurrence of weedy rice and control it in rice production, the spreading pattern and the indica-japonica geographical distribution were analized. We collected 205 accessions of 58 weedy rice populations from 58 sites at 13 cities in Jiangsu Province. The samples have been planted in the paddy field of Jiangpu Farm of Nanjing Agricultural University. 38 morphological traits and 6 Cheng's index traits were measured. Euclidean Distance clustering analysis showed that weedy rice followed a mutual-spread pattern in 13 cities. The indica-japonica geographical distribution of weedy rice showed that indica and indica-clinous type weedy rice distributed in 58 sites, accounting for 54.15% and 42.40% of the total samples, respectively. Japonica and japonica-clinous type weedy rice distributed in only 6 sites, accounting for 0.48% and 2.93% of the total samples, respectively. In addition, the geographical distribution comparison between the indica-japonica weedy rice and indica-japonica landraces showed no corresponding relationship. The vast majority of weedy rice in Jiangsu Province is indica type and japonica type weedy rice takes only a small proportion, which conforms to natural gene flow’s proportion between weedy rice and cultivated rice.