In response to changes in the shipping market and the demands of low-carbon transformation, shipping companies need to regularly optimize fleet deployment decisions for their routes. To enhance the objective of decisionmaking efficiency of shipping companies, a joint optimization model for fleet deployment and speed in liner shipping networks was formulated, and multiple factors such as ship type selection, cargo allocation across routes, and various green shipping measures were considered. Considering the inherent sequential decisionmaking characteristics of this model, a twostage interactive algorithm incorporating linear transformation and cascading increment strategies was proposed for efficient solution, and the accuracy and efficiency of this algorithm were validated through algorithm comparison and analysis. Compared to the algorithm that enumerates ship types, this algorithm improves solution efficiency by approximately 99% while achieving equivalent optimization results. Finally, taking the TransPacific shipping network as a case study to investigate optimal fleet deployment strategies. Results show that utilizing ships with larger container capacity while moderately increasing sailing speeds can significantly enhance operational profitability of carriers. The research findings can provide decision support for shipping companies to flexibly respond to market changes and efficiently formulate business strategies.