From 1904 to 1929, Donald MacGregor, a landscape designer trained at the Royal Kew Gardens in the UK, served as the Superintendent of Parks and Open Spaces of the Shanghai International Settlement. MacGregor's tenure in Shanghai marked a pivotal period in the development of the city's public green spaces, and his contributions were instrumental in shaping the city's early landscape architecture. By introducing modern landscape design notions, developing professional nurseries, and establishing a professional management and gardening workforce, MacGregor played a crucial role in the development of a systematic green space network. This research aims to provide a comprehensive analysis of MacGregor's impact on the establishment and evolution of the green space system in the early 20th century, examining both his professional background and the various ways in which his efforts transformed the city's public parks and open spaces. This study is based on an in-depth review of archival materials from the Kew Gardens Archives, the Shanghai Municipal Archives, and a range of online databases. These sources offer original documents and records that provide valuable insights into MacGregor's professional education and early career in the UK, as well as his work in Shanghai. The research not only examines MacGregor's contributions to landscape design and park planning, but also explores his influence on nursery development, road greening projects, and team management within the context of the Shanghai International Settlement. By analyzing MacGregor's work from his education in the UK to his key achievements in Shanghai, the research seeks to clarify the significant impact he had on the city's green space system, which laid the foundation for modern urban landscaping in Shanghai. The study highlights several key areas of MacGregor's contributions, focusing on the following major aspects: his innovative landscape design, the establishment and management of nurseries for plant cultivation, the planting of roadside greenery, and the formation of a multinational management team responsible for overseeing the green spaces. Each of these areas is examined in depth, alongside evaluations and assessments from contemporary government officials, professional institutions, and MacGregor's peers. These endorsements not only reflect the high regard in which MacGregor's work was held but also underscore the lasting impact he had on the development of Shanghai's green infrastructure. In conclusion, this study argues that Donald MacGregor's contributions to the development of the green space system were transformative and far-reaching. His professional expertise, innovative design principles, and managerial skills helped to shape the city's urban landscape and laid the foundation for the development of modern urban parks and green spaces in Shanghai. His legacy as a pioneer of early 20th-century landscape architecture in Shanghai has left an indelible mark on the city, and his work continues to be an important reference point for landscape designers and urban planners today. His work remains an essential part of Shanghai's urban heritage and serves as a reminder of the importance of thoughtful and sustainable urban greening.