Abstract: In order to predict the hydrodynamic characteristics of composite propellers, dimensional analysis was applied to identify the parameters affecting their hydrodynamic performance. Hydrodynamic similarity models for composite propellers were developed based on similarity criteria. The hydrodynamic performance, structural response and vibration modal characteristics of both the prototype and the model were analyzed using a bidirectional fluid-structure interaction method for composite propellers. The results indicate that the inflow velocity of the model, based on the Reynolds similarity criterion, is significantly higher than that of the prototype, making it difficult to achieve under conventional experimental conditions. This suggests that the Reynolds similarity model is unsuitable for predicting the hydrodynamic performance of composite propellers. Under the Froude similarity criterion, the model’s density must match that of the prototype, while the material’s elastic and shear moduli are reduced compared to the prototype. Since meeting both requirements in practical production is challenging, two non-standard Froude similarity models were developed by relaxing the criterion. In the Froude similarity model with relaxed elastic properties, the model exhibits greater stiffness, resulting in some deviation in hydrodynamic performance compared to the prototype. In the Froude similarity model with relaxed density requirements, the hydrodynamic performance of the model aligns well with the prototype, but there remains some discrepancies in the modal frequencies. The results based on the Mach similarity criterion show good agreement between the prototype and model in terms of hydrodynamic performance, structural response, and vibration modes. This demonstrates the applicability of the Mach similarity model for predicting the performance of the composite propeller prototype. The hydrodynamic similarity relationship between the prototype and model is established, providing theoretical support for the design and optimization of composite propellers.