This article explores the historical origins of the introduction of Japanese loanwords in China, tracing their routes of entry into the language and analyzing their impact on the formation of modern Chinese. Since the mid-4th century, when Japan had begun systematically to borrow Chinese characters to form their own writing system, the Japanese language was under strong Chinese influence. During the late Edo and early Meiji periods, however, Japanese scholars rendered a huge quantity of western publications into Japanese, hastening the modernization of the language. Indeed, the success of modernization in Japan after the Meiji Restoration reversed the cultural flow between China and Japan. Shocked and awakened by its half-century-long failure in foreign and domestic affairs, China began to modernize at the end of 19th century, dispatching students to Japan to learn western science and technology, as well as subjects in the western humanities. Their learning reached a Chinese readership through the medium of translation. For these Chinese translators, modern Japanese was an indispensable vehicle of western knowledge and linguistic transformation. Many Japanese-redefined and Japanese-created words were introduced in their translations with little modification, and these Japanese loanwords gained currency in Chinese. More significantly, the Japanese practice of creating new words to accommodate new knowledge influenced native linguistic practice, hastening the formation of modern Chinese. The introduction of Japanese loanwords into China also marked the beginning of a new period of Sino-Japanese relations, initiating a two-way cultural exchange between the two nations. 本文探讨日語外來語在中的來龍去脈，即追溯其進入漢語的渠道及其對現代漢語形成過程的影響。日本自四世紀中葉開始大規模導入漢字以形成其書寫系統以來，日語一直處於漢語的強大影響下。然而抵江戶幕末和明治初期，日本學者將卷牒浩瀚的西文典籍譯成日語，加速其語言的現代化過程。明治維新所帶來的日本現代化的成功逆轉了中日之間的文化流向。錯愕和震驚於半個多世紀在內外事務上的失敗，中國在十九世紀末開始派遣學生留日，希望通過學習西方科技文化知識帶動國家現代化。留日學生習得的知識通過翻譯傳給中讀者，對他們來說，現代日語成了傳播西方知識和促成語言轉型的不可或缺的工具。許多日語賦予新意和新造的詞彙幾乎未經處理就直接輸入，成為漢語的強勢語彙。更為重要的是，日語以新詞彙傳釋新知識的實踐影響了漢語的發展，加速現代漢語的形成。日語外來語的輸入還標志著中日關係新時代的來臨，在兩國之間開始了雙向型的文化交流。