Methane hydrate bearing soil is usually found under deep seabed and permafrost regions. It attracts research interest as a possible energy resource, but it also has potential impacts on climate change and geotechnical issues during methane gas production. Due to the limitations of laboratory studies, in this research, Discrete Element Method (DEM) simulations were performed to provide unique insights into the mechanical behaviour of hydrate-bearing sediments with pore-filling hydrate distribution. A series of drained triaxial shearing tests were systematically conducted to study the effects of hydrate saturation on the hydrate-bearing samples. It is shown that the peak shear strength increased and dilation was enhanced as hydrate saturation increased, especially when the hydrate saturation was above 20%. However, the critical state shear strength reduced slightly when hydrate saturation increased from 20%, with the dilation being reduced to zero in the critical state. The hardening effect of hydrate at the peak strength and the softening behaviour of samples in the critical state also reflected the peak and critical state friction angles. The strength of samples was enhanced with increasing confining pressure. It is found that for pore-filling hydrate distribution, the hydrate contribution to the strength of the sediments is of a frictional nature.