A discrete element method contact model building method includes: selecting a filling body in a disaster-causing structure to obtain a change rule of cumulative loss of the filling body; performing test simulation, and determining a relation function of each group of corresponding mesoscopic mechanical parameters in each time period and mesoscopic parameters of a DEM contact model representing a change rule of macroscopical parameters of the filling body; embedding each mesoscopic parameter relation function into an existing particle contact model, performing test simulation, and updating a fracture failure criterion of the contact model according to a corresponding relation of macro-mesoscopic strength during model failure; and based on a seepage failure indoor test, building a seepage failure discrete element calculation model, and simulating the seepage failure process of a rock and soil mass by using the obtained particle contact model and the fracture criterion of the particle contact model.