Abstract: Dry matter accumulation and effect of transplanting density on yield formation of Songjing 9 (super rice varieties) and Songjing 6 (conventional varieties) in cold region under different population conditions were studied. The results showed that: in a certain range of transplanting density, the population dry weight, export percentage of the matter in stem and sheath (EPMSS) and transformation percentage of the matter in stem and sheath (TPMSS) of Songjing 6 and Songjing 9 were increased with the density increasing. However, when the density was too large, it actually reduced. It was significantly positive correlated between harvest index(HI) and dry weight of panicle in the heading stage, dry weight of the whole plant in the mature stage. It was very significantly positive correlated between HI and dry weight of panicle in the mature stage. It was significantly positive correlated between EPMSS and dry weight of straw, dry weight of panicle in the mature stage. It was very significantly positive correlated between EPMSS and dry weight of whole plant in the mature stage. It was respectively significantly and highly significantly positive correlation between TPMSS and dry weight of panicle, whole plant dry weight in the mature stage. At the first accumulated temperature zone in Heilongjiang Province, the optimal planting density of Songjing 6 was 30cm×13.3cm, super rice Songjing 9 was 30cm×16.7cm.