The effect of chemical corrosion and natural joints on the damage characteristics and strength of rock masses is highly important for the construction of rock engineering and energy extraction. Therefore, the intact granite is processed into prefabricated fissured granite specimens with a fissure angle of 0°, 30°, and 45°. Chemical corrosion tests are then performed on the prefabricated fissured granites. The pH of the solution gradually becomes neutral; the mass loss of the granite specimens and the mineral compositions of the fissure surface are measured and analyzed. The scanning electron microscopy (SEM) and uniaxial compression tests are performed on the granite specimens after chemical corrosion. After chemical corrosion, the surface of the fissure becomes loose. The various mineral components of the specimens have been changed to different degrees or converted into other mineral components. The peak strength and elastic modulus of the prefabricated fissured granites with the three fissure angles present a clear decrease, as the time of chemical corrosion increases. The stress intensity factors at the fissured tip are also analyzed. The stress intensity factors of the specimens with a fissure angle of 0°, 30°, and 45° decrease from 0.017, 0.35, and 0.84 to 0.013, 0.30, and 0.74 MPa·m1/2, respectively, as the time of the chemical corrosion increases. And the chemical corrosion has the largest effect on the intensity factors of the specimens with a fissure angle of 45° among the three angles. These experimental results could improve the understanding of the long-term stability of underground engineering in the multifield coupling environment.