The gas hydrate′s filling process and microscopic distribution in the voids of sediments are observed by X-ray computed tomography (X-CT) imaging system.A new test technology is established,aiming at the difficulty in distinguishing the hydrate from the data images of sediment.The two kinds of methods,improving the density contrast between hydrate and solution or adding a hydrate grain as the calibration object,are improved effectively and achieve go od results.By the 2D and 3D images of X-CT scanning,the spatial distributions of free gas,sediment,water and hydrate could be clearly observed.Artificial CH_4hydra te is generated in the temperature-controlled high-pressure reactor and its forming process is recorded timely.The contrast of image data before and after hydrate formation shows that hydrate firstly emerges in sediment particle surfac e and gas-liquid interface,then gradually occupies most of the liquid phase space,and finally along with all of the sediment particles cementing together.The results show that X-ray computed tomography applied to the internal structure test of gas hy drate sediment sample,as well as the kinetic mechanism of gas hydrate growing in the sediment is feasible and effective.