Abstract: The application of vibroflotation without additional backfill treatment in silty fine sands is not so common．Combined with one key project in Shanghai，the engineering properties of saturated loose silty fine sands wereinvestigated through in-situ vibroflotation test． The effect of initial underground water level，dissipation regularity ofpore water pressure， effects of cone penetration test ( CPT) and standard penetration test ( SPT) were explored．Research shows that the treatment effect is not so good if the underground water level is too low，and the pore waterpressure generated during vibroflotation is related closely with the vibroflotation points and frequency，and foundationcapability is greatly improved after treatment． Summarizing the rest results，some rational construction techniques and parameters were suggested． Research testified the applicability of vibroflotation without additional backfill treatment in saturated silty fine sands．