Abstract: China's grain output has continued to increase since 2003. Identifying contributing and driving factors and quantifying their contribution rates to the increase of grain output (IGO) will help to make a correct agriculture policy to maintain or improve the grain production capacity. Using the statistics of outputs, sown areas, and yield (output of per unit sown area) of grain production and its composition crops (i.e. rice, maize, wheat, soybeans, tubers, and minor cereals according to National Bureau of Statistics of China), this paper analyzed the contributors and their contribution rates to IGO from crops and regional aspects. Furthermore, an algorithm was constructed to divide driving factors into sown area, yield, and adjustment of grain structure. The driving types of IGO were delineated according to the contribution rate of sown areas and yield for regions and crops. The results showed that the IGO were all from rice, wheat, and maize, which were considered as high yield crops compared to other grain crops. The largest crop contributor was maize, with a contribution rate of more than 50%. The output of minor cereals, soybeans, and tubers all declined during the period of 2003-2011, with the reduction rate of 25.7%, 17.4%, and 8.2% on sown areas for minor cereals, soybeans, and tubers respectively. Heilongjiang and Henan were the largest region contributors, whose cumulative contribution rate reached up to 35%. The top 13 provinces with the cumulative contribution rate more than 90% were mostly the major grain-producing provinces, except for Xinjiang. As a traditional major grain producing province, the contribution rate of IGO in Sichuan was just 1.6%. This value was roughly in line with the values of Shanxi, Shaanxi, and Gansu, which were all non-major grain producing provinces. At the national scale, the sown area of grain was the strongest driving factor, with a contribution rate of 46.3%, followed by yield, contributing 44.2% to IGO. Adjustment of grain structure contributed the remaining 9.5%, more than half of it coming from conversion of sown areas from soybeans to maize and rice. With respect to crops, the IGO in rice, maize, and spring wheat were mainly driven by the sown areas. The driving factors of the IGO in winter wheat were sown areas and yield, with yield slightly larger than sown area. At the regional scale, the sown area was the dominant factor to drive IGO in most of the main contribution provinces. Yield per unit sown area became the major driving factor only in Henan and Anhui. The contribution of sown area and yield were almost equal in Jilin and Hebei. Overall, China's IGO in the period of 2003-2011 belonged to the type of sown-area dominance. Henceforth, the potential of sown areas adjustment from low-yield crops to high-yield crops is limited by the consumption patterns of grains and the capacity of the international trade in grain. Therefore, in addition to stabilizing the sown areas of grain crops, improving grain yield is another important strategy to further stabilize and increase grain production capacity. The results will be able to provide a decision-making basis for China's agricultural policy adjustments.