The invention provides a system and a method for detecting an internal crack structure of rock, and belongs to the field of high-pressure detection. The system for detecting the internal crack structure of rock comprises a CT scanning apparatus, a high-pressure cabin and an air pressure apparatus; the CT scanning apparatus is arranged at the outside of the high-pressure cabin; the CT scanning apparatus is used to perform X-ray detection on a to-be detected sample; and the air pressure apparatus is connected with the interior of the high-pressure cabin via a pipe and is used to inject a gas into the high-pressure cabin and meter the gas flow. By utilizing the system and the method, when the gas is injected, CT scanning detection is performed on the sample. Under the condition of no damage to the detected object, in the form of a two-dimensional cross-sectional image or a three-dimensional stereo image, the structure, the compositions, the texture and the defect status of the interior of the detected object can be clearly accurately finely visually displayed in a multilayer way.