The Japanese Emperor Hirohito accepted the Potsdam Declaration on 14 August 1945 represented the Japanese government announced the unconditional surrender. Based on the declaration, the process of the Allied occupation of Japan from 1945 to 1952 started. The period from 1945 to 1952 was special not only because it was the time of the allied occupation of Japan and also the period of Cold War. Japan as a defeated country in the WWII was occupied and the U.S. government had a special role in Japan. The Supreme Commander for the Allied Power (SCAP) had critical role in Japan in this period and it marked the change of Japan and the U.S. also made important change on the immigration policy. The U.S. occupation allowed the interracial marriage between the G.I.s and the Japanese women. Japanese war bride was the product of the occupation. They witnessed the immigration law reform, the racial problem in the society and the cooperation during the cold war. In this paper, I argue that Japanese war brides as the subject in the reform of the immigration laws. The implementation of different public laws, from only allowing non-Asia war brides to open to all war brides within the deadline show the improvement in the racial limitation requirement. The Immigration and Nationality Act of 1952 and 1965 further reduced and eliminated the national origins quotas. Asians can therefore immigrate to the U.S. I also explain the racial ideas in the U.S. society by analyzing the bride schools. The war brides were encouraged to participate in the bride school before leaving Japan. They learned the history of the U.S., the culture and society of the U.S. and other skills as housewives and mothers. They were trained to match with the expectation of the U.S. society. I also analyze “assimilationism” and immigration policies. The “assimilation” of the Japanese war brides in Bride school can represent the ideology of immigration in the situation of the postwar society. The immigration laws before 1965 still contained the national origins ideas, which the Soviet Union used to attack and criticize. However, the U.S. occupation allowed the cooperation with the Japanese government. The “assimilation” of the Japanese war brides provided a special scene in showing the encounter of “assimilationism” and immigration law reform. The Japanese war brides witnessed the change in the immigration laws, “assimilationism” and Cold War policies. The Japanese war brides were the subjects in viewing the reform of the immigration policies. Using them to review the process can provide a different angle to evaluate the Cold War situation.