Pipeline transportation of CO2, as one of the key links in the CCUS(Carbon Capture, Utilization and Storage) industry chain, plays an increasingly important role in the development of offshore CCUS. The low-temperature brittle fracture and dry ice blockage caused by the release of high-pressure dense phase CO2 from pipelines seriously affect the operation safety of CO2 transportation pipelines between offshore platforms. In this paper, the depressurization model of dense phase CO2 subsea pipeline between offshore platforms has been developed using LedaFlow dynamic simulation software. The changes in temperature and pressure profiles of the pipeline, and release rate for depressurization in winter and summer environment offshore have been analyzed. The influence of different initial transportation pressures and volume, and pressure relief rate on the low-temperature fluid of the pipeline has been compared. The results indicate that the low temperature of subsea pipeline caused by depressurization in winter is lower than that in summer, so it is recommended to carry out CO2 pipeline pressure relief in summer. Under the lowest ambient temperature conditions in winter, appropriately reducing the discharge aperture can effectively avoid low temperature in the pipeline caused by significant changes in pressure and temperature profiles along the pipeline. The results can provide reference and guidance for the actual depressurization operation of offshore dense phase CO2 transportation pipelines.