Parks are important components of the built environment in the settlements and should be designed and improved to protect the functions in the long term. The aim of this study is to develop a method that quantitates the sustainability levels of park designs. The study was carried out in three parks, namely Şehitler Park, Osman Arslan Park and Atatürk Park, in Kalecik district of Ankara. First of all, the criteria determined by the SITES rating system for the land design were examined and regulated by considering regional conditions. In this context, four main criteria, including soil and vegetation, material selection, water, human health and well-being, and 30 sub-criteria were evaluated. The Simos procedure was used to assign weight to criteria and the 5-likert scale was used to establish the suitability scores. Sustainable Landscape Design Index (SLDI) was calculated for each park and each sub-criteria with various equations. SLDI values expressing sustainability levels of parks were given and interpreted in tables and diagrams. Accordingly, one of the parks has the highest SLDI average in terms of the main criterion of the water and the other two of the soil and vegetation. SLDI values for human health and well-being are at the lowest level in all parks. When the sub-criteria were examined, it was seen that the three parks reached the highest SLDI value in three different sub-criteria, including the suitable plant use, reducing the use of wood material produced from threatened species and an efficient irrigation system, and the lowest SLDI value in the sub-criteria of providing smokeless airspace. The study revealed a comprehensive, comparable and reproducible index method that quantitates the sustainability levels of existing parks. The method is expected to be used as a measurement tool in the creation of new parks suitable for sustainable design and the renovation of existing parks.