As competency-oriented reform continues to reshape basic education, curriculum innovation in primary and secondary schools is gradually shifting from optimising disciplinary content to restructuring learning processes and curriculum organisation. Interdisciplinary project-based learning (iPBL) embeds authentic problems into classroom contexts and emphasises sustained inquiry, collaborative learning, and evidence-based expression, making it a promising approach for bridging disciplinary knowledge and real-world problem solving. However, current practices in primary and secondary schools often reveal limited depth of curricular integration, misalignment between project goals and disciplinary objectives, activity-oriented implementation, and assessment practices dominated by final products. Drawing on relevant theoretical perspectives and authentic school-based cases, this study examines the design logic, enactment processes, and learning outcomes of iPBL and proposes a curriculum renewal framework aligned around goals, tasks, evidence, and scaffolds. The findings suggest that clarifying disciplinary roles, strengthening formative assessment based on learning evidence, and establishing sustainable teacher collaboration are essential for high-quality iPBL implementation, with strong potential for broader application in integrated practice, science education, and school-based curriculum development.