Low temperature seriously affects the growth and distribution of rice.Weedy rice may evolve out new cold tolerance mechanisms in the natural selection process of rice field, which could provide new gene sources to breed cold tolerance cultivars. 75 weedy rice populations and their coexisting cultivars were collected and germination experiments under 8 different treatments were processed, which were with or without breaking dormancy, normal temperature（25℃）or low temperature（15℃）, 7days or 14days , respectively. The results showed the germination ratio of weedy rice was extremely significant correlation with the germination of their coexisting cultivars under the treatment without or with breaking dormancy. Germination ratio of weedy rice with breaking dormancy was significantly or extremely significantly higher than that without breaking dormancy. Whether without or with breaking dormancy ,the results showed that cold tolerance of weedy rice was stronger than coexisting cultivar, which indicated weedy rice might had evolved a novel mechanism of cold tolerance at 15℃. Furthermore, the germination ratio of weedy rice and their coexisting cultivars at 25℃ was significant or extremely significant correlation with latitude, which showed that germination ratio increased and dormancy turned weaker with decreasing latitude.