AbstractDeep cement mixing (DCM) is an environmentally friendly technique for offshore ground improvement without dredging or much disturbance to the marine ecological system. Several field construction factors can influence the unconfined compressive strength (UCS) of cement-stabilized soil. In this study, key construction factors are evaluated referring to site investigation records, construction records, and quality test results of a large offshore DCM construction project. The key factors were attributed to geological conditions, construction procedures, and curing conditions. Specific field construction factors include fluctuations of tidal level, original soil type, volume fraction of injected water, volume fraction of injected cement slurry, injection rate of cement slurry, penetrating and mixing time per meter, curing age, and moisture content. The importance of these construction factors on the DCM strength has been quantified using a statistical method based on construction records. The injected water volume and original soil type are noted to be the two most dominant factors on the UCS of the treated soils. Longer mixing time improved the strength of the treated soils.