This paper discusses the rationale for establishing the interval from the Gabo Reforms (1895) to the liberation from Japan (1945) as the modern Korean language period for teaching the history of Korean language or the life history of Korean language. Such setting of this period arose from the critical awareness regarding the school grammar curriculum which defines modern Korean language as the language developed during the era between the Imjin War and the end of the Gaehwa period. The issue of differentiating by period the history of Korean language in the school grammar curriculum is seen as a problem that arose from a simplistic use of the term “modern” as it is applied in the life history of Korean language. To properly establish the modern period of Korean language, a balanced perspective is required regarding the concept of history which is affected by opposing approaches, such as those of positivist and relativist historical views and micro and macro histories. In addition, since the modernity in modern history has freedom and equality language life inequality in the history of language should become the key perspective. From this standpoint, the establishment of modern Korean language must be looked at of the human agent as its basic attributes, the overcoming of contradictions such as from the basis of written language rather than spoken, and the identity of spoken and written language which holds the issue of equality in language life should become the key yardstick for establishing the period of modern Korean language. Hence the Gabo-Reforms which occasioned King Gojong’s Royal Decree on Korean Language (1895) and the publication of the DoknipShinmun(1896) should be set as the starting point of modern Korean language .Moreover, since Koreans fully became the principal agents of Korean language and the Hangeul-only Law was enacted in the wake of the liberation from Japan(1945), the liberation should be taken as the line that divides modern Korean from contemporary Korean language