This paper aims at decomposing China's grain output changes into three terms, namely area sown effect, pure yield effect, and cropping pattern adjustment effect. Furthermore, the paper analyses the impact of shifts in cropping pattern on water and land use in China's grain production. An index decomposition analysis framework is employed to calculate the corresponding contributions. The research relies on grain production data at both national and provincial levels during 2003-2012. The results show that besides the effects of area sown and pure yield changes, cropping pattern adjustment has also played an important role in promoting China's grain production, with a contribution of over 15 per cent during 2003-2012. Moreover, such changes enabled to save about 6.8 million hectares of sown areas and 31.06 billion m3 of water in grain production (if compared to the case without cropping pattern adjustments). However, these effects vary across regions: Southeast China experienced land-saving and water-using changes, while other regions underwent land- and water-saving changes. In general, China's grain output growth has increased the total amount of land and water needed, implying more severe resource constraints in the future, especially in the northern part.