One major challenge in agro-meteorological research is to accurately predict the impacts of global climate warming on future agricultural production. Towards this effort, the effects of climate warming over the past decades need to be assessed. In this study, we analyzed the effects of the climate warming on crop planting, structure and yield in five Northwestern provinces of China with a focus on Gansu utilizing accumulated temperature (≥10℃, AT), accumulated negative temperature (<0℃, ANT) and crop data collected from 1981 to 2003. The analysis led to the following conclusions: (1). Climate warming is the main driving force for the expansion of winter wheat toward North and West, for the rapid increase in cotton planting acreage, and for the expansion of annually multi-crops areas towards north and higher altitude. (2). Climate warming is the direct cause for early seeding of spring crops, and prolonged growth duration for thermophilic crops and shortened duration for overwinter crops. (3). Climate warming is largely attributable to the dramatic increase of cotton yield.