The utility model discloses a borehole finishing tool and a drill string, and belongs to the technical field of petroleum and natural gas drilling. The borehole finishing tool comprises a body 1, cutting edges 2 and cutting teeth 3, wherein the body 1 is provided with a hollow tubular structure; the cutting edges 2 are arranged on the outer wall of the body 1; a first part of the cutting edge 2 close to the upper end of the body 1 has a stepped structure; a second part of the cutting edge 2 close to the lower end of the body 1 has a stepped structure; the step structure of the first part and the step structure of the second part are respectively provided with multiple steps, the heights of the steps of the first part are gradually increased from the position close to the upper end to the position far away from the upper end, and the heights of the steps of the second part are gradually increased from the position close to the lower end to the position far away from the lower end. And the cutting teeth 3 are arranged on the stepped structure of the first part and the stepped structure of the second part. By adopting the utility model, the technical problem that the comprehensive drilling cost is increased due to well wall finishing in related technologies can be effectively solved.