Abstract: Cyclic pore water pressure could be produced by the action of the wave load in the offshore sand foundation.It was very important for coastal and offshore engineering to study the mechanical behavior of sandy soils under the action of cyclic pore water pressure.Based on the results of consolidated undrained triaxial tests on Fujian standard sand,the parameters,ratio of consolidation stress,relative density and frequency,were studied,and they obviously affected deformation of saturated sand under cyclic pore water pressure produced by water pressure controlling instrument.The experimental results indicated that the specimen had a large deformation when the ratio of consolidation stress and frequency were larger and the relative density was smaller.Finally,the curves of axial strain and dynamic pore water pressure coefficient were figured and analyzed.