This article focuses on the role of European missionaries in the formation of modern Chinese lexicon from the viewpoint of the diachronic evolution of the Chinese language. From the beginning of the 19th century, European missionaries contributed to the unification of modern written Chinese by devoting themselves to translation and invention of new lexicon, especially in the area of mathematics, sciences and politics. At the beginning stage of their activities, the missionaries transcribed spoken Chinese including several dialects. This transcription made the spoken Chinese more prominent and it in turn gave rise to new written form of Chinese called “modern Chinese.”