The unification of language is a symbol of national unity. To a very large extent, the National Language Movement(NLM)in the 1940s in Macau was a kind of overseas Chinese affairs, aiming at the unification of Chinese compatriots. Bits and pieces related to NLM retrieved from record archives and past newspapers, although not systematic, are valuable historical information. By fitting all pieces together, the author is able to draw the contour of NLM in Macau starting from the outbreak of the anti-Japanese war to the post-war years. During the Japanese invasion, Macau was a ″neutral area″ and was free from the ravage of war. At that time, some Mandarin courses for the public and for teachers were supported by the Ministry of Education, serving the purposes of educating the illiterate public and nurturing the Mandarin teachers. The Mandarin courses for teachers did provide some training for hundreds of teachers. However, given the poor education condition at that time, the impact of these classes was very limited, let alone the Mandarin courses for the public. Nevertheless, the Dayong Private School for Mandarin Training run by Guan Yushu offered Mandarin courses for more than 40 times during the period between 1938 and 1945. It shows that NLM was never interrupted throughout these years. After the victory of the War of Resistance, the establishment of the Macau Association for Chinese NLM brought the movement to a new page in Macau. This association, being a locomotive of NLM in Macau, was closely related to the Kuomintang(KMT)Macau Branch. The objectives of this association were clear. The missions stated in its registered articles of association were implemented as planned. Their enthusiastic attitude was reflected in a series of promotion events, including Mandarin courses, the Mandarin week, the Mandarin speech contest, teaching Mandarin through radio broadcasting. More importantly, some of these activities were extra-curricular activities for primary and secondary students, and Mandarin was promoted through school education. Bound by the key principle of assisting the nation to promote NLM, many local organizations swarmed to offer Mandarin courses for their members even though the supply of qualified teachers was very limited at that time. Judging from the fact that some local schools, the Chinese Chamber of Commerce, the Chinese Women's Association, the KMT Macau Branch and etc. all offered very intensive evening Mandarin courses for the public consecutively, we can conclude that there was a strong demand for such Mandarin courses in Macau. In 1947, a small-scale primary school using Mandarin as their main medium of instruction was set up. The school authority secured great support from the Overseas Chinese Affairs Committee and this might indicate some symbolic meaning for Mandarin teaching in Macau. However, at that time, local schools by and large were not ready to use Mandarin as their medium of instruction at all. In general, this article was written on the basis of the primary sources of information. The author believes that the wide coverage of the relevant information and the meticulous details of many activities will extensively portray a full picture of NLM in Macau in the 1940s.