This study investigated and analyzed various library classification systems and related literature in order to suggest some modifications and expansion of the Dewey Decimal Classification, the 23rd edition (DDC 23) in the area of immigration policy - an interdisciplinary subject - for the best information organization and services. First of all, definitions and scopes of the immigration policy were dealt with and then primary subject areas of it were selected. And then, DDC, Library of Congress Classification, Korean Decimal Classification, and Universal Decimal Classification were compared and analyzed according to the structures, headings and characteristics. Finally, modified classification schedules in immigration policy of the DDC 23 - the most frequently used one with an regular revision was proposed with their principles and main schedules with an auxiliary table. It can be used for an effective information organization in immigration policy area and it will be useful for many libraries and research institutes on immigration policy.