This study is to understand North Koreans' language assimilation process in South Korea. 10 North Koreans participated in the interviews. Most of North Koreans seriously recognize language differences and put their effort to overcome the differences. They think that proper language use is very important in their adjustment process. Most of them are not satisfied with their current job but very confident of better future. According to the results form this research, North Koreans who arrived earlier perform better in the language assimilation process on the whole. Also, it is found that North Koreans with higher educational background and stronger will to adapt themselves score better in the test of language assimilations.