Two collinear fractures were prefabricated on plate shale using a high-pressure water jet technique. These prefabricated fractures were then filled with cement. Uniaxial compression tests were conducted to study the crack propagation characteristics of rock specimens containing closed collinear fractures, and the crack propagation process was recorded using a high-definition camera. The results show the following: (1) Two types of crack were observed in the mechanically damaged specimen: tensile cracks represented by wing cracks and antiwing cracks and compression-shear cracks represented by secondary coplanar cracks and compression cracks. (2) Different branch cracks that emerge at different times. (3) If the space between fractures is shorter than the fracture length, crack band can be formed through crack coalescence in the mode of shearing coalescence, tensile-shear-tensile coalescence, and shear-tensile-shear coalescence; otherwise, it will not occur; if equal, crack coalescence will occur in partial rock specimens. (4) The initial crack angle of wing cracks ranges from 46° to 86°, averaging at 66.26°. (5) The deterioration degree of compressive strength of prefabricated fracture–containing shale is larger than its elasticity modulus. (6) From the perspective of fracture mechanics, the crack initiation sequence, the extending angles of wing crack and antiwing crack, and the advantageous crack angle of collinear crack model were analyzed.