Many cities promote community-based day care center in Taiwan owing to community care service becoming the major service of long-term care policy. Nevertheless, environmental function of dementia day care center was unclear and lack of design guidelines. The purpose of this research was to study the assessment indicators of environmental quality in order to provide the basis of environmental development for dementia day care center. Systematic literature review to establish the frame and indicator of assessment and Delphi to process experts panel reaching reliability and validity of indicator contents were applied as research methods. The results of this research showed that the assessment indicators of environmental quality for dementia day care center included surveillance facility and safety protection, construction of reminiscence setting, multiple activity spaces for occupational therapy, reality orientation and sign system, spaces arrangement for social activities, decrease of illusion and hallucination in the environmental design and construction of wandering path and space. These 13 assessment items and 72 assessment indicators are available for the basis of environmental assessment during Ministry of Health and Welfare implementing the assessment of dementia day care center, as well as become the reference for building design criteria.