This paper focuses on the calculation model and method for the subsidence of ripraps in the foundation trench of a gravity wharf. By a compression test of full-scale riprap blocks in the foundation trench，this paper obtains the stress-strain relationship of the block stones under repeated loading and unloading and then uses the relationship to build a calculation model for the subsidence of the ripraps in the foundation trench of the gravity wharf. Taking into account the construction process of the gravity wharf，this paper proposes a calculation method for the subsidence of the ripraps in the foundation trench and obtains the key parameters of the model by regression with the data observed in the actual engineering field. The results show that the calculation results of the proposed model are consistent with the observed data.