Abstract: The fully internal crack is created in the Brazilian disc based on the 3D-ILC method, without any effect on the surface. The uniaxial compression experiments are performed on the Brazilian discs with internal cracks at different angles. The experimental results are compared with the existing literatures. The propagation of the fully internal crack, the distribution of the stress-induced birefringence, the initiation of the crack and the failure stress and the fracture surface characteristics are investigated. Then the numerical simulations are carried out. The results show that: (1) The validity of the 3D-ILC is proved in the fracture mechanics researches. (2) The stress birefringence of the cracked specimen is discontinuous at the internal crack. (3) Compared to the intact specimens, the internal cracks greatly reduce the strength of the Brazilian disc, with decrease of 10.7%, 60.6% and 89.2% for the specimens with 30°, 60° and 90°. The stresses of crack initiation are 100%, 11.7% and 15.6% of the failure stress for the specimens with 30°, 60° and 90°. (4) The internal crack is penetrated by the primary crack for the Brazilian disc with crack of 30°. The mode I-II 3D wing cracks occur at the crack tip, while the mode III cracks occur at the sides of discs with internal crack of 60°. The primary crack is mode I crack for the disc with internal crack of 90°. (5) Numerical simulations are carried out on the Brazilian discs. The results may provide experimental support for the corresponding theoretical researches.