The problem of horizontal cracks in rock-bolted crane girders in underground powerhouse of a hydropower station was very prominent with a lot of penetrating cracks even in construction period, posing safety risks on the long-term stable operation. According to the design and construction condition, the bearing behaviors of the girders with different horizontal cracks distribution were studied by numerical approach and the deformation and forces of crane girder were analyzed. Results show that the horizontal cracks could reduce the local stiffness of girders and increase the deformation. Tensile stress concentrated near the crack tip, and the distribution of tensile stress widened, with some exceeding the allowable range. Nevertheless, the horizontal crack has little effect on the safety factor of the anti-sliding stability. Since the rock-bolted crane girders must be in long-term safety, reinforcement in the horizontal crack concentrated area is needed.