Abstract: The force transferring rule of contact forces inside two-dimensional granular packs arranged symmetrically and orderly was investigated.Using the probabilistic method,a force transferring model was constructed and a corresponding transmission equation was put forth,which were not the traditional elasticity theory predictions a parabolic equation but a parabolic equation supporting a granular description.The model and equation reveal ‘arching effect’ and ‘two peak phenomenon’ resulted from arching effect’ and was consistent with the experimental results qualitatively.