The research entitled The Implementation of Open Green Space (Park City) in Sleman City With The Validation of Law Number 12 of 2012 About The Planning of Spatial in Sleman Regency. The problem formulations in this research are to see how the implementation of public green open space in Sleman regency with the validation of law Number 12 of 2012 about the planning of spatial in Sleman regency, and the attempt of government to create the green space (park city) in Sleman regency. This legal research was conducted by data from both primary data and secondary data. The data were collected by interview and library study, and analyzed as quantitative. The result of this research shows that the public green open space in Sleman regency is appropriate to the law number 12 of 2012 on planning of spatial in Sleman regency which is 30,03% fromthe provision minimum 20% of the area that available in Sleman regency.