Abstract: In order to improve the bearing capacity of sea sand foundation in China, a treatment method for curing of sea sand foundation using polyurethane has been studied. The cyclic traffic load tests on the pure sand and reinforced sand were carried out by using hollow cylinder apparatus under different dynamic stress ratios and loading frequencies. A hollow cylindrical sample preparation method which is suitable for polyurethane rapid and efficient curing sea sand was innovatively designed for the study. And the micro-reinforcement mechanism was analyzed based on SEM results. The experimental results show that: The strain curve and pore pressure development of pure sand are divided into three development trends with the change of dynamic stress ratios, the critical dynamic stress ratio η' obtained by the test is 0.33. The smaller the frequency f under different frequency conditions is, the more obvious the cumulative effect of cyclic load is, the more obvious the development of strain and pore pressure are, bounded by the condition f=1.5 Hz, showing two development trends. The axial cumulative strain of the cured sea sand under the two sets of loading conditions did not exceed 0.7%, and the pore pressure development limit did not exceed 20 kPa. In some conditions, pore pressure eventually turned to be negative, resulting in shear dilatation. The analysis of SEM results shows that the curing agent takes up part of the pores in the sand after reaction. And as a consequence, the curing agent and sea sand forms a stable spatial structure, which leads to an increase of the resistance of particle rearrangement, thereby greatly improving the mechanical properties of the cured sample.