At present, the messy and dirty phenomenon of Taiwan's external wall of building that is lacks the explicit maintenance and appraisal of methods and standards. The research designated the buildings sets up the surface that located along Sec.3 and 4 on Chung-Hsiao East Road in Taipei. On the spot investigation in external wall, those are messy and dirty. Attaches at present situation, to collect entire related literature, analysis present management regulation and utilizes methods and AHP experts questionnaire. The important first position in the discussion is that to improve the present question about saving present outer wall. The appraisal factor about the outer wall messy and dirty weight divided into: First, Public security, city's appearance look, economical performance following development for appraisal target main construction. Second, the structure broken soil, the danger of falls, the security to escape, the outer wall decoration material, the outer wall window, the advertisement things, the window with iron grating, the air-conditioning plant, the equipment pipeline, the economic value promotion, the degree of aging improvement and how to saves the energy. Third, weighting factor of the destruction for beams, columns, balconies and windows, etc. To establish datum of important item is the external wall maintenance appraisal target. This research results are: 1.Induce the outer wall messy and dirty phenomenon the state. 2. Inside and outside the statistical survey scope wall messy and dirty phenomenon quantity and the proportion, as reference of datum for the maintenance renewal. 3. Drafts simply and objective outer wall maintenance appraisal target, as evaluates the tool for the improvement renewal.