English has become the international language of science, especially in China. Researchers in China have been increasingly publishing in the English language, as evidenced by the exponential growth of publications by China in major bibliographic databases in recent decades. Nevertheless, there has been limited research on the exact pattern of languages used by Chinese researchers due to a lack of infrastructure covering publications in both English and Chinese produced in China. In this study, we present preliminary findings from our project analyzing all research outputs funded by the National Science Foundation of China (NSFC), the leading government research funder in natural sciences and engineering in China. We strive to understand what languages Chinese STEM researchers use in journal and conference publications, how language use varies by research domains and projects, and how the trends evolve. Our preliminary results show that English was the most popular language in STEM research in the 2010s, and its popularity increased during this decade. Moreover, the use of the English language is also positively correlated with the seniority of project PI as embedded in project classes. Our preliminary results provide the basis for more granular analyses and more constructive conversations about the use of languages in scientific research in China.