As a basic principle of international water law, the principle of equitable and reasonable utilization has the normative basis of treaty law and customary law, and can guide the use of transboundary waterways and the allocation of water resources. However, the abstractness and ambiguity of the principle reduces the certainty of its application. The application limitations of the principle of equitable and reasonable utilization are manifested in the immature theoretical foundation, the difficulty in unifying the concept, and the nonexclusive consideration of multiple factors without prioritization. The reflection on the principle of equitable and reasonable utilization requires full respect for the natural characteristics of transboundary watercourse, compliance with the principle of not causing major damage and the principle of international cooperation, clarifying the priorities of relevant considerations, and promoting the establishment of a consensus of interests of watercourse countries, thus achieving the equitable and reasonable utilization of the boundary watercourse by basin states.