The soft and thick clayey soil layers are commonly distributed in the nearshore waters of the Yangtze River Estuary, and their engineering characteristics have a direct impact on the construction of major projects.Piezocone penetration test (CPTU) is an effective in-situ testing method.By interpreting the test data, it can achieve the purpose of soil classification, soil layer division, and obtaining soil parameters.Due to the variability and regional characteristics of soil, it is necessary to establish a formula for the relationship between CPTU index and soil properties in an engineering site.Based on a regulation project in the nearshore waters of the Yangtze River Estuary, this paper carries out seabed mode cone penetration test and laboratory soil test, and establishes a formula for the relationship between modified cone resistance qt1 and soil gravity density γ.The range value and total average value of calibrated CPTU cone factor Nkt for clayey soil in the Yangtze River Estuary are calibrated based on consolidated quick direct shear, quick direct shear and unconsolidated-undrained triaxial tests.When there is a lack of site calibration results and geotechnical test results, using cone factor Nkt and the formula for the relationship between qt1 and γ can effectively solve the undrained shear strength of clayey soil in the engineering site, and provide a certain interpretation basis for clayey soil with similar physical properties in the coastal area of the Yangtze River Estuary.