Abstract: The twin seedlings come from M_(1) generation of dry seeds of inbred line 478, which are irradiated by~(12)C heavy ion produced by HI-13 tandem accelerator of China (Institute) of Atomic Energy. By means of random amplified polymorphic DNA(RAPD) method, the results show that the bands of the large seedling of the twin seedlings are different from that of the small one, and there are different bands compared with their parents, inbred line 478. The (above) results show the twin seedlings are a new variety of inbred line 478 in the molecular levels.