The present invention relates to a downhole drilling tool system of torque self-balancing and belongs to a technical field of drilling engineering equipment. The drilling tool system consists of an assembly of internal and external drill bits, power components, a pressure adjustment system for internal and external drill bits, a mud circulating system, and an unfreezing system. The present invention employs a dual drill bit of internal and external drill bits to crush rocks by inverse rotations, which realizes the drilling with slight disturbing to the surrounding rock; the torque self-balancing of the drill bit and the power system is realized as a whole without the torque effect to the upper drilling tool by utilizing the stator group and the rotor group of the power motor to drive the external and internal drill bits respectively; it is only necessary to trip the winch apparatus for the drilling tool on the ground to realize the normal operations of drilling, tripping, and logging-while-drilling by integrating the power source, mud circulating system and logging system, etc. into the drilling tool; the winch hoists up the drilling tool to remove rock particles at the sticking point by alternative positive and reverse rotations of the drill bit for unfreezing in order to realize the unfreezing when got stuck.