The invention discloses a soil mass shearing rupture failure testing device which comprises a base, a front baffle plate, a thrust providing device, a load sensor, a displacement sensor and a data acquirer. A soil mass shearing rupture failure testing method comprises the following steps of: (1) putting a test sample on a second slide track between the front baffle plate and the thrust plate; (2) starting the thrust providing device, applying a pressure to the test sample, and recording; and (3) generating a curve graph of the stress and the deformation of the test sample. The test sample is put on the base between the thrust plate and the front baffle plate, the front baffle plate and the thrust plate are arranged at the left and right sides of the crack of the test sample, the thrust plate applies thrust to one side of the test sample, opposite to the thrust plate; and the test sample is blocked by the front baffle plate so as to prevent the test sample from sliding. with the crack as a boundary, the left and right sides of the test sample takes are subjected to two forces in opposite directions till the test sample is damaged. The forces acting on the test sample in the test sample can be read through the load sensor, the deformation position can be read through the displacement sensor, the test process is simple, and the read test result is not influenced by the operation error and the friction and is high in accuracy.