Triaxial tests of the sandy gravel with four different densities have been performed under different confining pressure in order to investigate the effects of relative density upon strength and deformation behaviour of the sandy gravel. The test results show that, within the range of the relative density of the experiments, the hardening characteristic of the stress-strain curves have become distinct with the increase of the confining pressure when the relative density is low; and the stress strain curves appear as strain softening regardless of the value of confining pressure when the relative density is high. Different degrees of the dilatancy are showed during the lab tests. With the increase in the density, the values of φ and φ0 increase, and the values of c and Δφ decrease, therefore, a functional relationship between them has been established. The values of E1 and Bt show a linear growth with the increase of Dr because the secant modulus E1 and the volume modulus Bt would increase with the increase of Dr.