The Purpose of this paper is a study on the characteristics of Campidoglio hill plan by Michelangelo. 1. The plan of the Campidoglio hill is composed of the harmonized and united space, in spite of the existing conditions of a steep flight of land, a irregular site shape, a building of each other different dimension and form. And it is newly changed by site left through the modification of existing building elevation, utilization of existing building for new planning, connection with existing building and newly planned building from plaza composition of trapezoid form. 2. The concept of planning of the Campidoglio hill is planned by compromising for requirements of Baroque after Renaissance which urban planning characteristics of Baroque is as the relation with urban street through a inclined stairs and process such as street-approach stairs-plaza-symbol of inside plaza-building. 3. The section plan of the Campidoglio hill is planned by which can be easily approached to the plaza through the inclined stairs of gentle angle from street at the center east-west direction of main axis such as main axis, utilizing the existing site shape, and it is composed of the convex shape ascending gently at the center central part of the plaza. 4. The plan of the Campidoglio hill is composed of the elation with the axis of existing Senatorio palace, building planning of perfect balance, plaza composition of reversed trapezoid form bybuilding planning, central concentrated planning of buildings surrounding plaza. 5. The three palace of the plan of the Campidoglio hill is composed of the concept as theater which the stage background forms the front elevation of Senatorio palace higher two palace and the wings of either side of stage form the front elevation of Conservatori palace and Nuovo palace, surrounding three palace elevation around plaza of trapezoid form.