Impacts of climate change on agriculture has received wide concerns globally, yet a number of questions such as how past climate change affected the crop yields, which climatic variables were the main contributor for observed yield reduction remained unanswered to date, particularly in developing countries. Information about the climatic risks posed on crop growth, and yield responses to the specific climatic risks is prerequisite for understanding the underlying mechanisms of climate change impacts and devising appropriate adaptation strategies. This study first identified the changes of growing-season climatic variables (temperature, precipitation, and solar radiation) from 1982-2006 for China's maize production. Using the relationships between changes in survey maize yield and climatic variables and their spatial variations, we investigated and untangled the impacts of different climatic variables on maize yield. Our analysis demonstrated that the growing-season temperatures, including daily maximum, minimum and mean temperatures, exhibited significant increase during 1981-2006, indicating the potential climatic risks for maize growth in China. Growing-season diurnal temperature range, precipitation and solar radiation also exhibited detectable changes, but limited to small parts of the maize area. During 1981-2006, there were significant negative correlations between national maize yield and temperatures (include mean, maximum, and minimum temperatures). Maize yield in some maize areas also exhibited linear correlation relationship to growing-season diurnal temperature range, solar radiation, and precipitation. With a 1℃ warming in growing-season temperature, 1℃ increase in diurnal temperature range, a 10% decrease in radiation and precipitation, much of the maize area showed detectable yield response to these changes. Maize experienced depressed yield to the 1℃ warming in growing-season temperature, denoting by roughly a quarter of China's maize area exhibiting depressed yield and an estimated reduction of 25.1% across the regions that have detectable negative yield responses. The four climatic variables have diverse impacts on the maize yield in terms of the magnitude of yield change and the spatial variation of yield response. We identified the key climatic factor for observed maize yield change for all maize area. Temperature appeared as the first key climatic driver for maize yield change in over 40% maize area, while diurnal temperature range acted as a main player in 23% maize area. Radiation and precipitation shared a small and similar portion of maize area for playing as the key climatic variables for the yield response. We recognized the uncertainties in our study some of which came from reliability of data resource and the use of statistical method. However, this study provided first hand information on maize yield response to historical climatic risks, which advanced the understanding of underlying mechanism of climate change impacts on China's maize production and assisted the projection of maize yield for future climate change.