Two-dimensional physical model tests are designed to study the soil motion characteristics around offshore windfarm monopile foundations. Periodical loading induced by wind, wave, current, and rotor motion in the field is simplified to lateral cyclic loading exerted on the top of monopile models in the tests. PIV and PTV technology were used to measure the motion process of vibrating monopile and its surrounding soil. The properties of the soil subsidence and convective motion around the monopiles under different test conditions were obtained. The results show that each characteristic scale of soil deformation approximately has a linear relation with the loading frequency and displacement amplitude of pile-top. The characteristic scale of soil deformation increases with the increase of the loading frequency and the displacement amplitude. At the quasi-equilibrium stage, the depth and width ratios of the subsided hole and convection area are 0. 24-0. 34 and 1. 47-2. 34, respectively. The convective motion of soil is driven by the frictional shear stress generated by the monopile-soil interaction. The velocity of the sand convection motions is around 10^-4 cm/s, which is generally three orders of magnitude smaller than the vibration velocity of monopile.