The Yellow River Estuary is a typical constructive delta with a complex sedimentary structure. To analyze the physical, mechanical properties, and structural characteristics of the surface sediments in the delta, reveal the sedimentary environment and avoid geological hazards, cone penetration test (CPT) is used for nautical in situ testing and evaluating effective internal friction angle (φ'). Four typical areas formed by the diversion of the Yellow River Estuary in different periods are selected as the research objects to perform the in situ CPT, particle size analysis test, scanning electron microscopy, and triaxial test, building calculation model. The main conclusions are as follows: (1) The sediment given priority to are silt and silty clay, where the stratigraphic distribution difference is more significant, accompanied by soft interlayer or alternating layers of hard. (2) Hard soil in the sediments cause abrupt changes and fluctuations in the cone tip resistance and sleeve friction resistance. (3) The empirical formulas proposed by Berezantsev, Khristoforov, and Golubkov, Kulhawy and Mayne, and Mayne are used to predict φ' and the effect of inversion is good. (4) The coefficients of formulas are significantly improved, modified according to site variability.