A simulation experiment for the increments of 0%, 20%, 40%, 60%, 100% summer rainfall was set up in the sandy grassland of Yanchi in Ningxia province. Soil temperature, together with soil moisture, was measured from 2012 to 2013 in order to probe into the effects of summer rainfall change on soil temperature in the sandy grassland ecosystem. It was found that the daily changes of soil temperature tended to be as a sine curve, and it's CV and amplitude were not affected by summer rainfall but dependent on the seasonal variation. The phase of daily changes of soil temperature was affected by summer rainfall amount and dependent on the seasonal timing. Seasonally, 20% and 60% increases of summer rainfall indicated a contrasting (i.e., the former to increase and the latter to decrease) effect on soil temperature, which was independent on seasonal timing. Whereas, the effects of 40% and 100% increases of summer rainfall were found to depend on the seasonal timing. From 2012 to 2013, the summer soil temperatures (e.g., July and August) were affected remarkably by the summer rainfall increases, whereas the autumn soil temperatures (e. g., September and October) were affected little. It was suggested that the impacts of summer rainfall changes on soil temperature depended much on a threshold of rainfall amount, and also to some extent depended on the seasonal timing changes in the sandy grassland ecosystem.