A drilling fluid channel structure of a core drilling rig includes a fluid channel activation module, a pressure relief module, a flow diverging and blocking module, a driving fluid channel and a cooling fluid channel. The fluid channel activation module, the pressure relief module and the flow diverging and blocking module are connected sequentially from the rear to the front. The driving fluid channel and the cooling fluid channel are connected at the rear side thereof to the flow diverging and blocking module. The driving fluid channel includes a driving section located between a stator and a rotor of a driving motor. The driving fluid channel is provided with a driving fluid outlet at the front side of the driving section. The cooling fluid channel passes through a layer disposed between an integrity-preserving compartment and an outer barrel.