The conflict resulted by the relation between old city structure and new construction of historic citiesis a leading theme of the academic debates of the architectural and urban planning fields of Italy. Theacademic debates on it have continued in years from the second half of the 19th century to the 1970s.The urban conservation policy based on the historic zone strategy in urban planning system wasestablished in a problem solving process. But the main point of the academic debates has not beenintroduced to Japan sufficiently in the past. This study is aimed at re-examining the formation processof the historic zone strategy of Italy using the reference of documents which belong to the period fromthe 1920s to1970s and also tracing its role of the urban planning system.