Abstract: In order to ensure the quality of subgrade construction, this paper takes cement modified silty clay and silty clay as the research object. Through the indoor tri-axial shearing and wave velocity detection test, the factors affecting the compressive strength and shear wave velocity of the subgrade are studied, and the correlation between them is proved, which provides a technical basis for roadbed quality inspection. The study found that under certain test conditions, the change tendencies of compressive strength of the subgrade and the shear wave velocity are basically the same. The strength and wave velocity increase with the increase of cement dosage and age. When the clay content is 18%~22%, the strength and wave velocity of the improved soil are larger. The research results provide technical basis for roadbed quality detection.