The purpose of this study is to find out the commercialization characteristics of 2nd class residential district in innercity railway station area as basic research to protect urban residential area against the pressure of commercialization. Through the research that are based on literature, field survey and urban planning map, it analysed the commercialization characteristic of selected three sites under similar urban condition; to be a nearby subway station and to be a famous commercial street in site, etc. The consequences of this study are summarized as follows; First it finds the commercialized lots in all blocks that adjoin blocks of upper class zoning. Second it is in inverse proportion between the commercialization of lots and the distance from subway station to residential block. Third, the corner lot of a block and the access road directly connected collector road are very important factors to spread commercialization to residential area. Finally, it finds the difference of the commercialization degree of 2nd class residential zone according to arrange main commercial street and the 2nd class residential block; vertical arrangement and horizontal arrangement.