Abstract: Project-based learning serves as a crucial implementation form for instruction in the field of "Synthesis and Practice" within primary school mathematics. As a streamlined version of project-based learning, micro-project based learning is characterized by its small scale, short cycle, and subject focus, making it particularly suitable for teaching in the upper primary grades. Accordingly, this study constructs a micro-project based learning model for primary school "Synthesis and Practice" from the perspective of mathematical culture, integrating the five characteristics of mathematical culture with the four essential elements of micro-project based learning. Taking the lesson "Save Water" as an example, it proposes four practical pathways: bridging the "cultural cognitive gap" by constructing a view of teaching content grounded in mathematical culture and emphasizing historical inheritance; breaking through "disciplinary barriers" by building a view of learning activities based on interdisciplinary integration and emphasizing the synergistic development of cognition and aesthetics; transcending "virtual situations" by forming a view of social practice rooted in real-world problems and emphasizing value identification; and resolving "unitary evaluation" by establishing a view of student development assessment based on multicultural attributes and emphasizing the balance between norms and innovation.