The purity of seeds produced in three-line hybrid rice breeding is a critical factor influencing seed quality and planting efficiency. Based on years of practical experience in seed production, this study systematically analyzed the main factors leading to decreased purity in three-line hybrid rice seeds, including low parental seed purity, improper setup and management of isolation zones, foreign pollen contamination from scattered grains, mechanical mixing, and abnormal climatic conditions. On this basis, we review the current application status of seed purity assurance technologies, explored the underlying causes of low seed purity during production, and proposed comprehensive improvement strategies centered on purification and rejuvenation, intelligent impurity removal, and digital field management. The results showed that through the integrated application of key technologies—such as three-level purification and rejuvenation, molecular marker-assisted impurity detection, and four-dimensional pollination regulation—hybrid seed purity can be stably increased to above 99.0%, with seed yield improved by 15.0%-20.0%. This paper provides both theoretical foundations and practical approaches for promoting the standardization and industrial development of seed quality in three-line hybrid rice production.