The invention discloses a mechanical property testing device which comprises a fixing device, a first stress application device and a second stress application device. The fixing device is provided with a fixing base and a counter-force base. The fixing base and the counter-force base are fixed to the ground separately. The fixing base is used for fixing a sample. The counter-force base is connected with an upper beam stress application device and a lower beam stress application device. The first stress application device is provided with an angle clamp, a first connecting component and a first loading component, the angle clamp is used for clamping the sample in an angled mode, the first connecting component is connected with the angle clamp and the first loading component, the first loading component provides loading force, and the first loading component is rotationally connected with the counter-force base; the second stress application device is provided with a clamp, a second connecting component and a second loading component, the clamp is used for clamping the sample, the second connecting component is connected with the clamp and the second loading component, the second loading component provides loading force, and the second loading component is rotationally connected with the counter-force base. The device can achieve multi-point, multi-direction and multi-angle combination loading testing.