The Sino-U.S. relation has been deemed as one of the most important bilateral relationships of the 21st century. However, this relation is being undermined due to the growing tension between the two countries in recent years, sparking people’s worries about the potential military conflicts between the two major powers. With the endorsement from the U.S. government, the “Annual Report to Congress: Military and Security Development involving the People’s Republic of China” (China Military Power Report or CMPR in short) proves to be an optimal window for observing the military development of China and the attitudes of the U.S. However, little attention has been paid to CMPRs from the perspective of critical discourse analysis (CDA), which is quite abnormal given that CDA is designated for investigating political or ideological issues embedded in discourses. Therefore, this study, combining CDA with corpus linguistics (CL), aims to identify the major concerns and the diachronic changes embedded in CMPRs. Analysis of the top keywords of CMPRs shows that China’ great advances in military power and increased military activities during the last two decades can be confirmed, that the People’s Republic of China (PRC) seems to be acknowledged as the sole legitimate representative of China by CMPRs, and that China’s military power development is increasingly related to the U.S. while the role of Russia changes greatly and is fading away in the military development of China. Analysis of the collocates of China identifies a number of major concerns of CMPRs. In addition, it reveals that more concerns are directed to China’s military strategies and territorial disputes while China’s military arsenal and the Taiwan issue are comparatively receiving less attention, and that the negative attitude held by CMPRs towards China’s military strategies and its moves against Taiwan is persistent. As for the collocates of America, the analysis indicates that the confrontation and the communication between China and the U.S. are increased over the years, and that the prosody of CMPRs changes from negative in the Jiang Zemin period to relatively positive in the Hu Jintao period, and then to negative in the Xi Jinping period.