Abstract: The mechanical parameters of hydrate-bearing sediments are the key parameters for the stability evaluation of hydrate formation. The hydrate-bearing sediments in Shenhu area of South China Sea contain large amounts of clay mineral. It is of great significance to understand the effects of clay minerals on the mechanical properties of sediments for hydrate mining. Based on triaxial compression simulation in the PFC code,we first analyzed the mechanical effects of clay mineral to the sediment without hydrate. Secondly,we analyzed the cementation effect of hydrate to mineral grains and the influence of confining pressure on the mechanical properties of the sediment. Our results indicated that the deviator stress-strain curve of the model without hydrate shows obvious strain hardening characteristics. The clay mineral content,grain shape and grain arrangement have significant effects on the triaxial compression characteristics of the sediment. The increase in the content of clay mineral has a significant effect on reducing the mechanical strength of sediments. The peak strength and elastic modulus of the sediments with strip-shaped clay grain are significantly higher than those of the sediment with round-shaped clay grain,which are related to the average co-ordination number in the microscopic view. The directional arrangement of the strip-shaped clay grains makes the mechanical parameters of the model to be anisotropic. The cementation effect of hydrate on the grains can significantly increase the peak strength and elastic modulus of the model. With the increase of the interparticle cementation degree and the decrease of confining pressure,the failure mode of the hydrate-bearing sediments changes from plastic failure to brittle failure.