Starting from the fundamental connotation of commemoration, the concept of “intentional monuments” and “historical monuments” of Alois Riegl is used to interpret and analyze the monumental spaces in Shanghai’s modern parks, comparing the emergence, strengths, weaknesses, and interconversion relationship of the two types, interpreting their “symbolic commemorative significance” and “ontological commemorative significance” in the process of conservation and renewal, and defining and identifying the characteristics of their formation. Taking Fuxing Park and Huoshan Park as examples, this paper analyzes the changes in the project process, the difference and reasons between the design intention and the actual operation, and discusses the transformation of the two significance in the specific transformation and the spacial reconstruction. This paper argues that the distinction and interpretation of the two significance can expand the role of commemoration in the conservation and renewal of historical parks and further understand and clarify the contents worthy of conservation, renewal, and activation. As a kind of historical public space, historical parks record the collective history of social groups in the creation of parks and the traces of their use, and this record helps future generations to build up a historical understanding of parks, thus giving rise to ontological significance; historical parks also perpetuate the memory of people, events and social life in history, generating symbolic significance in order to satisfy this spiritual need. The two significance are inseparable and complementary in the park. Strengthening symbolic significance can enhance people’s memory of the park, but at the same time, the material ontology should be preserved as a stable foundation for historical continuation; while in cases where material preservation is emphasized, it should not fall into fixation and rigidity, and should actively explore the potential of commemorative significance from material history, stimulate the vitality of the park and the birth of new commemorative spaces.