This study conducts longitudinal sectional inspections on grouting sleeves from dismantled precast segmental bridge piers in a Shanghai project to analyze construction quality and the impact of potential defects. Through longitudinal sectional inspection methods, key indicators—including grouting compactness, anchorage length of reinforcement bars, and centrality—were meticulously evaluated across 10 grouting sleeve samples. The results indicate that the grouting material exhibits excellent compactness, with all mechanical properties meeting design specifications and regulatory requirements, confirming overall construction reliability. Although localized deficiencies such as slightly reduced anchorage length and minor deviations in reinforcement centrality were observed, existing research suggests negligible effects on structural bearing capacity and deformation resistance. The study concludes that current construction techniques largely satisfy quality standards but recommends optimizing grouting material formulation, refining construction processes, and adding threaded structures to sleeve exteriors to enhance concrete bonding strength. This research provides empirical test data supporting the safety and durability of grout-sleeve-connected piers, supplementing insights into internal defects undetectable by non-destructive testing methods.