The invention discloses a direct shear test system for anisotropy of geosynthetics and an implementation method of the direct shear test system. The direct shear test system comprises a test bed rack, a slewing bearing, a dial, a lower shearing box, an upper shearing box, a vertical loading device, a horizontal loading device, a guide rail, a displacement sensor, a slewing bearing control device and a bearing plate, wherein the guide rail and the displacement sensor are arranged on the test bed rack; the dial and the slewing bearing control device are respectively arranged on the slewing bearing; the vertical loading device is arranged on the slewing bearing sequentially through the bearing plate, the upper shearing box and the lower shearing box; the lower shearing box is driven to rotate by the slewing bearing; the cross section of a geosynthetic which needs to be subjected to a shear test is round, and the diameter of the geosynthetic is same as the outer diameter of the lower shearing box; the horizontal loading device is connected with the slewing bearing and can slide on the guide rail. According to the direct shear test system for the anisotropy of the geosynthetics, the technical problem that the engineering practice cannot be truly reflected by the interface mechanical characteristics of the geosynthetics and fillings which are obtained in the test in the prior art is solved.