Abstract: In order to evaluate the effect of hydrate formation on the mechanical strength of hydrate-bearing sand, a series of triaxial compression tests are conducted on the samples prepared by means of two different methods, namely, the partial water saturation method (A method) and the dissolved gas method (B method). The experimental results show that the strength and stiffness of the samples formed by A method increase sensitively with the saturation of hydrate, whereas those prepared by B method keep almost constant when the saturation of hydrate is less than 19%, and then increase significantly when the saturation of hydrate is higher than 27%. The results imply that the mechanical behaviors of the hydrate-bearing sand depend upon both the content and the distribution of hydrate in the pores. The hydrate-bearing samples tend to dilate when the saturation of hydrate increases. In addition, an analysis of experimental results of the samples prepared by the A method shows that the cohesion of the samples increases with the saturation of hydrate, while the frictional angle keeps practically constant.