Abstract: An analytic method of fabric theory for granular materials was presented to study the creep deformation mechanism for high rockfill dams.Macro mechanics and deformation response of rockfill assemblies were discussed from the microcosmic point view.It was shown by recent studies that only the void factor and the dry density could not describe the discrete characteristics of rockfill materials completely.The analytic method of fabric theory included not only the mechanical meaning of the above macro indices but also the distributing state of rockfill in space.Fabric tensors included geometical characteristics of rockfill granules,interaction among granules and distributing state of rockfill granules in space.The osculating relation existed between rockfill fabric tensors and stress tensors,which had been theoretically proved.So the creep mechanism and the deformation law of rockfill could be gained from the variation of fabric tensors,and thus the creep mechanism of rockfill might be revealed from the microcosmic view.