The invention relates to a visual natural gas hydrate sediment mechanical property testing apparatus, belonging to the field of the measurement of basic natural gas hydrate physical properties. The visual natural gas hydrate sediment mechanical property testing apparatus mainly comprises an automatic-pressing triaxial apparatus main machine, an axial loading system, a confining pressure control system, a backpressure control system, a temperature control system, a data collection system and an X-ray CT (computed tomography) imaging system. The low-temperature high-pressure hydrate triaxial apparatus is organically combined with the X-ray CT imaging system, so that the testing on macro and micro mechanical properties of natural gas hydrate sediments can be synchronously carried out. The visual natural gas hydrate sediment mechanical property testing apparatus can simulate a stress state of a real reservoir stratum, macro and micro mechanical property data of the natural gas hydrate sediments can be acquired, the important significance on disclosing a deformation mechanism of the natural gas hydrate reservoir stratum and a triggering mechanism of geological hazards such as submarine landslide caused by the decomposition of natural gas hydrate can be realized, and an important guiding function for safely and high efficiently exploiting the natural gas hydrate can be realized.