Abstract: In order to study the deformation characteristics of caissons buried in soft clay under long-term horizontal load, three groups of model tests are designed and done. The capacity of caissons is first identified, then further tests are carried out to study the load-deformation curves, distribution characteristics of soil pressures in the passive area, displacements at top of the caissons, short-term and long-term displacement characteristics of soils in the passive area. Based on the test data, the ideal elastic-plastic of p-y curve is revised according to the loading time and magnitude. The results calculated by the revised formula agree with the test data, and the case studies show that the revised formula can provide theoretical and design guidance for the deformation calculation of caissons in soft soil areas.