Abstract: Piezocone penetration test(CPTU) is one of the most widely used in-situ testing methods at present,but CPTU cannot in-situ measure the soil density,which is the most basic physical index of soil. Density piezocone penetration test(DCPTU),incorporating the nuclear densitometer into the piezocone penetration system,is a new in-situ testing method that can simultaneously measure the cone resistance,sleeve friction,pore water pressure and density during the penetration. In this paper,the testing apparatus and density testing theory of DCPTU are introduced firstly. Then,the reliability of measuring density of sand,clay,lumpy fill and seabed sediments by DCPTU is evaluated by comparing with laboratory test results. The difference between measured and actual density of heterogeneous strata is analyzed and a method for deducing the actual density profile is proposed. The engineering applications of DCPTU,including identification of soft interlayer,evaluation of liquefaction potential of sand,examination of the effect of ground improvement,detection of spaces of lumpy fill,and investigation of the thickness and density distribution of fluid mud layer,were summarized. Finally,the development trend and application prospect of DCPTU in measuring maximum shear modulus of soil,in situ evaluating soil structure and in situ testing physical and mechanical properties of unfavorable ground are forecasted.