The aim of this paper is to examine the Japanese Language educational policy to Mongolia from 1930s to 1940s. It will begin by analyzing the history about the language education policy in Japanese colony, and then I will examine the expansion process, the influence of Japanese Language educational policy to Mongolia in Manchuria. The point I want to make is that : the Japanese educational policy to colony is "Japanese Language only", but it didn't fit to Japanese propaganda in Manchuria. So, to Mongolia Japanese educational policy is different. In elementary educational institutions, the policy is "Japanese Language plus Mongolian Language". But in secondary educational institutions, is the same as the policy as other colonies.