Software cost estimation is an important task in software project development and management. Based on the research results of renowned economist Boehm, this article constructs the COCOMOII model, which summarizes software cost estimation into five steps: workload estimation, proportion factor estimation, workload multiplier estimation, development progress estimation, and currency cost estimation, and presents them in a flowchart. Based on the COCOMOII model, this paper takes the “Land Sea Intermodal Logistics Information Platform” developed by the author for a certain company as an example to illustrate the process and method of software project cost estimation based on the COCOMOII model. In practical application, it is necessary to fully absorb the advantages of other estimation methods, enhance the flexibility, scalability, and operability of the model, in order to demonstrate strong vitality and make software development cost estimation closer to the actual value.