Objectives  The optimal selection of ship's main engine is a problem worthy of further study, and also a complicated problem on multi-attribute decision making.

  Methods  The criteria system of optimal selection of a ship's main engine was proposed by deeply analyzing the influence factors of the ship's main engine selection. The objective weight was calculated by entropy weight method. And the subjective weight was calculated by deviation entropy model. Then an interactive weighting method was presented to calculate the comprehensive weight of the ship's main engine selection criteria system, which unified the objective weight and the subjective weight. Finally, the evidential reasoning approach was used to fuse information to sort and select the best one from the options.

  Results  The method above was proved to be effective and correct by taking the optimal selection of the main engine in the ship building project of a waterway administration as an example. What's more, the influence rule that the interval selection has on utility value of evaluation results, is further explored.

  Conclusions  The results show that the combination of interactive weighting and evidential reasoning can provide theoretical support for ship main engine type selection design。