The invention discloses a three-direction loading large-scale three-dimensional analog simulation test sampling method. The method includes the steps: (1) inclining a test piece case; (2) obtaining prefabricated test piece stress measuring points to arrange the position of a pressure sensor; (3) obtaining the optimal proportion of similar materials of each stratum; (4) sequentially containing each stratum until all rock stratums are contained in the test piece case; and meanwhile, arranging the sensor and an oil sac in a test piece; and (5) enabling the test piece box to recover to the horizontal position after the similar materials are dried. By means of the method, complex distribution of coal seam stress in different top plate moving stages during underground excavation can be simulated, manufacturing large-inclination-angle ore bed test pieces is more convenient and effective, rock mass can be stored under the conditions of three-dimensional stress in the whole mining process, and underground space excavation under more operating conditions can be researched. In addition, the aboveground height of the whole system is decreased, and the system is lower in manufacturing cost and more stable.