Long-distance water diversion projects are characterized by extensive routes, complex geological conditions, and involvement of multiple specialized disciplines, making quality control during the construction phase a core challenge for supervision. This study, based on an inter-basin ecological water replenishment project in Inner Mongolia Autonomous Region (with a total pipeline length of approximately 134 km), systematically analyzes the quality control difficulties faced by project supervision in key aspects such as long-distance pipeline installation, special geological section construction, tunnel lining, and multi-segment coordination. To address these challenges, the study proposes a dual-control mechanism of "full-process on-site supervision and critical process witnessing," innovatively introducing digital solutions like remote video monitoring via wireless bridges and concrete mixing plant production data collection systems. By statistically analyzing quality defect data and application outcomes during project implementation, the study quantitatively demonstrates the significant role of digital monitoring in quality traceability and process control. Practical results show that the systematic countermeasures proposed effectively enhance engineering quality management, providing valuable reference for similar projects.