Abstract: Base on the Hertz contact mechanics, assuming the materials as elastic-plastic hardening, and considering the adjustment and release of contact stress on the plastic contact region, a new granule elastic-plastic contact theory has been suggested. Then, the elastic-plastic impact among granules has been investigated under the material’s quasi-static hypothesis. At last a corresponding formula is given and compared with other models. The results have shown that the force-deformation relation locates between the curves following Hertz theory and Thornton theory according to new model. It also clearly shows the curve will approach closer to the Hertz solution when the hardening coefficient becomes higher and to the Thornton solution when hardening coefficient is lower, so the Thornton model is a special case of this model. In fact, the impact pressure predicted with the new model is far smaller than the Hertz elastic solution and more conformable to reality.