Abstract: The royal parks in London were the first parks in the world to be open to the public, and collectively make up a significant component of the British garden history. An examination of the process of opening up these parks contributes to further exploring the public attributes of designed landscapes and the concept of public parks. Through a diachronic analysis, this paper points out that parks were open to the public when the concept of “park” was initially introduced into England. Since the 14th century, they evolved into private hunting grounds for the royal families. Then, these parks were opened to the designated privileged stratum and wealthy classes. Finally, under the pressure of the masses, they were entirely opened to the public in the late 19th century. Hence, these parks have experienced a process from open to closed, to semi-open, and to fully open. The opening of parks was closely associated with the transformation of the nature and function of these parks, and aimed to maximize profits for the royal families.