Abstract: To investigate the influence of wind and wave conditions on ship navigation performance along ocean routes and to improve the scientific basis for speed regulation and energy-efficiency evaluation, a coupled resistance model incorporating calm-water resistance and wind-wave added resistance is developed in this study. Based on the proposed model and the direct power method,ship speed loss rates are calculated. Taking the route from the Suez Canal to Shanghai as a case study,five key sea regions are identified,including the Red Sea entrance,the Arabian Sea,the Bay of Bengal,the Malacca Strait-northern Indonesia region,and the South China Sea. Seasonal mean meteorological data from the ERA5 dataset spanning 24 years are employed to calculate the total added resistance and speed loss rates for both outbound and inbound voyages in different seasons,thereby revealing the spatial distribution characteristics of ship speed loss. The results indicate that the Arabian Sea experiences the highest added resistance during inbound summer voyages,with speed loss rates exceeding 11% in certain areas. In contrast,the Malacca Strait-northern Indonesia region exhibits relatively small annual resistance fluctuations and consistently low speed loss rates throughout the year. The findings provide quantitative references and data support for route segmentation,speed regulation,and voyage optimization along long-distance shipping routes.