Most of the engineering rock masses contain a variety of different levels of geological tectonic joints and weak planes, which can weaken the rock strength. The rock masses containing joints have completely different mechanical properties with the intact ones. Through loading failure tests on the rock masses containing two intermittent joints of prefabricated of different spacing, the differences between jointed rock mass and intact one were studied. The research shows that: 1. Comparing with the intact rock mass, the stress-strain curve of jointed one has a relatively large fluctuation near the peak, it isn’t smooth, and there's a reduction in the stage of plastic flow after yielding; ultimate strength decreases obviously, joint depth has a great impact on strength, and there's no necessary link between ultimate strength of rock mass and joints spacing. 2. When the loading is failure, the elastic and deformation modulus of rock mass decrease obviously comparing with those of the intact rock mass, which tend small generally with the increment of joints spacing, however, they have a relatively complex relation and it isn't linear. 3. The failure characteristics of jointed rock mass are different from those of the intact rock mass, failure planes are relatively complex and no longer single shear or complementary shear ones, which presents that shear failures occur along the end of prefabricated joints with few extensional cracks; the spacing of prefabricated joints have a great impact on the failure pattern of rock mass. The research results can provide certain references for the mechanical parameters selection of jointed rock mass of engineering design and numerical analysis.