For the improvement of problematic soil of soft marine deposit, in Hong Kong airport project, we carry out the experiment of laboratory mixing and site trial for marine deposit improved by deep cement mixing(DCM)with wet method for the first time. From testing results, we research the important influence factors, including soil properties, cement dosage, curing age, etc., on the unconfined compression strength(UCS)of laboratory and in-situ cement-soil mixtures, and find that the UCS of mixtures increases evidently with increasing of binder dosage and curing age, and obtains the correlation between mixture UCS and curing age. The research results provide good engineering reference for further application of DCM method used for soft ground improvement in Hong Kong.