Abstract: The continuous large vibration will be generated during the construction of the pile, resulting in the cumulative deformation of soil and the increase of the excess pore pressure, which eventually leads to the decrease of soil strength. Taking the west side of Raffles Square as an engineering case history, studies of the law of the clay slope's strength variation in the process of construction vibration are carried out. The vibration and shock of the anti-slide piles were tested by using the vibration meter and the ultra-low frequency sensor, according to the dynamic stress characteristics of the vibration, the static and dynamic triaxial tests were carried out to simulate the in situ stress state and stress path of the soil unit, in addition a test method has been developed. At last the reduction of soil strength under the action of dynamic stress during construction was analyzed. The analysis results of field vibration tests show that the maximum vibration velocity of the surface is up to 2 cm/s, as well as there is still a vibration at 26 m distance away from the pile, of which the velocity is approximately 0.16-0.24 cm/s. At the same time, with the increase of pile foundation construction, the vibration effect of soil is enhanced. Except for the above findings, it is also found that in the consolidated undrain condition, the results of static and dynamic triaxial tests show that when the total stress intensity envelope under different confining pressures was made, the dynamic strength of the soil is obviously lower than that of the static strength. And the relevant indexes data from results are obtained, and the soil body total strength index C_cu=49.5 kPa and φ_cu=17.0°are measured. The influences of pile foundation construction on soil strength are different according to different experimental rules. The test slope is clay conforms to the experience curve of soil strength reduction. Considering that the influences of the vibration force will increase slope sliding force and affect the strength of the soil, the comprehensive strength reduction coefficients will be taken as 0.7-0.8.