Abstract: 【OBJECTIVE】Boss biomass production and yield formation characteristics were observed using two super hybrid rice combinations bred in Jiangsu Province, the factors limiting yield potential in super hybrid rice was studied. 【RESULTS】The results showed that, super hybrid rice had good production capacity either at common density or low density. High yield was mainly attributable to the big panicles. But the seed setting characteristics were not promoted observably and the percentage of ripened grain was lowly level yet. Conventional variety used as contrast also showed high yield at common density, but low yield at low density. The biomass production of super hybrid rice, particularly that after heading was remarkably higher than that of Shanyou 63, the weakness in biomass production of normal hybrid rice was improve obviously. The translocation rate of storage carbohydrate in stem and sheath of super hybrid rice had no significant changes compared with common and low density, the translocation type was showed significantly. 【CONCLUSION】The key points to further improve in conclusion, yield is to make a breakthrough in seed setting characteristics under the conditions of higher total spikelet number has been obtained, to improve significantly the percentage of ripened grain. Relatively condign low density may increase the biomass production after heading and improve the seed setting characteristics.