Objectives  As many factors influence decision-making in the course of warship water reuse scheme optimization, and such factors cannot be fully quantified and sequenced, it is necessary to build a scientific and reasonable optimization evaluation model.

  Methods  Based on the grey analytic hierarchy process (AHP) and Delphi method, an evaluation index system for warship water reuse schemes with a hierarchical structure is constructed for the first time. The grey evaluation method of whitening weight function is used to quantify the evaluation elements and carry out the comprehensive evaluation of different schemes.

  Results  The calculation results show that the obtained comprehensive evaluation results are reasonable, and the consistency test of the total hierarchical ranking meets the index requirements.

  Conclusions  Based on expert judgment, grey analytic hierarchy process can comprehensively adopt opinions from all aspects, reduce the arbitrariness and subjectivity of judgment, and improve the scientificity and rationality of scheme selection. It is suitable for optimal decision-making of multi-schemes and multi-objectives water reuse system design for warship.