As global climate issues intensify,society is paying more attention to low-carbon development.Carbon accounting is crucial for achieving carbon peaking and neutrality,with carbon emission calculation being a key part.Land reclamation projects,known for their large scale and large engineering volume,have significant carbon emissions.As one of its core structures,the steel cylinder is of great significance for carbon emission measurement.This study uses the carbon emission factor method to calculate and analyze carbon emissions during the construction stage of a steel cylinder island-wall structure in a certain project.It also compares these emissions with those of slope-type and bucket-foundation breakwaters.The results show that carbon emissions during the construction phase of steel cylinders mainly come from materials,accounting for 94%,and steel is the main source of carbon emissions.Indirect emissions from material use are higher than direct emissions.Transport ships and crane ships rank among the top two in terms of carbon emissions in ship machinery equipment.The carbon emissions per meter of the main material for the steel cylinder breakwater structure are 77 t,which is higher than the 69 t of slope-type breakwaters but lower than the 103.5 t of bucket-foundation breakwaters.This study provides a scientific basis for the formulation of engineering carbon reduction strategies and helps promote the development of land reclamation projects towards low-carbon direction.