Abstract: To elucidate the reproductive constraints contributing to the endangerment of Rhododendron yuefengense G. Z. Li and support evidence-based conservation, the flowering phenology, pollination biology, and breeding system of wild populations in Cat’er Mountain National Nature Reserve, Guilin, Guangxi, were systematically investigated. Field observations and experimental approaches were employed to assess flowering dynamics, pollen viability, stigma receptivity, pollen-ovule ratio (P/O), outcrossing index (OCI), and reproductive outcomes under controlled pollination treatments. Results showed that: (1) R. yuefengense reached full bloom in mid- to late May, with a total flowering period of approximately 40 d. Bombus species were identified as the primary floral visitors; (2) pollen viability was highest on the first day of flowering, reaching 83.06%; (3) the OCI was 5, and P/O ratios ranged from 244.70 to 2 558.60; (4) artificial pollination experiments confirmed the absence of agamospermy and wind pollination. Natural fruit set reached 50%, whereas cross-pollination achieved 80% fruit set. The results indicate that R. yuefengense adopts a mixed mating system combining partial self-compatibility with enhanced reproductive success through outcrossing, and depends on Bombus species for effective pollination under natural conditions.