The present invention discloses a multi-circulation-flow-channel drilling system and drilling process for large-size wellbore hard rock drilling. The drilling system includes a downhole air hammer ground manifold and device, a gas lift manifold and device, a drilling drive apparatus, a multi-circulation-flow-channel drilling tool and a mud circulation device, wherein both the downhole air hammer ground manifold and device and the gas lift manifold and device are correspondingly communicated with the multi-circulation-flow-channel drilling tool by means of the drilling drive apparatus, respectively; and the mud circulation device is connected to the drilling drive apparatus by means of an erosion-resistant gooseneck and a sand discharge pipeline. The system combines advantages of both gas lift reverse circulation sand discharge and a closed reverse circulation air hammer, and can greatly reduce a gas injection amount while ensuring drilling efficiency, which is beneficial in reducing device investment, reducing an occupied area of a site, reducing demands for power and a drilling fluid, and reducing fuel consumption.
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