Rockfill materials obtained either by blasting rocks or collected from the riverbeds are used in the construction of Rockfill dams. In this paper, Prediction of strength parameter on two rockfill materials is investigated. Drained tri-axial tests have been conducted on various sizes of rockfill materials used in the two dams using a relatively smaller size triaxial cell. Tests data has been analyzed and effect of size of rockfill material and that of triaxial cell on strength parameters has been studied.