A self-drilling screw, comprising: a screw head; and a screw rod extending outwardly from the screw head, the screw rod formed with a drill bit section at one end opposite to the screw head, a drill tail section adjacent to the drill bit section, and a screw thread section adjacent to the drill tail section, wherein the drill bit section is provided with at least two first cutting edges extending and intersecting at a chisel edge P, and at least one first chip flute located at a position respectively between the first cutting edges and extending from the chisel edge P toward the drill tail section, the drill tail section is provided with at least two second cutting edges extending helically toward the screw thread section, and at least one second chip flute located at a position respectively between the at least two second cutting edges and extending helically toward the screw thread section, and the screw thread section comprises a screw thread extending helically toward the screw head; wherein each first chip flute and the second chip flute form a connection at a joint between the drill bit section and the drill tail section; a first chip flute width D1 of each first chip flute is less than or equal to a second chip flute width D2 of each second chip flute, and the first chip flute width D1 is greater than or equal to one-half of a diameter D3 of the screw rod; characterized in that the second chip flute width D2 of each second chip flute is tapered off toward the screw thread section, and a difference between the second chip flute width D2 of each second chip flute adjacent to the drill bit section and the second chip flute width D2 of each second chip flute adjacent to the screw thread section is within 0.5 mm. a screw head; and a screw rod extending outwardly from the screw head, the screw rod formed with a drill bit section at one end opposite to the screw head, a drill tail section adjacent to the drill bit section, and a screw thread section adjacent to the drill tail section, wherein the drill bit section is provided with at least two first cutting edges extending and intersecting at a chisel edge P, and at least one first chip flute located at a position respectively between the first cutting edges and extending from the chisel edge P toward the drill tail section, the drill tail section is provided with at least two second cutting edges extending helically toward the screw thread section, and at least one second chip flute located at a position respectively between the at least two second cutting edges and extending helically toward the screw thread section, and the screw thread section comprises a screw thread extending helically toward the screw head; wherein each first chip flute and the second chip flute form a connection at a joint between the drill bit section and the drill tail section; a first chip flute width D1 of each first chip flute is less than or equal to a second chip flute width D2 of each second chip flute, and the first chip flute width D1 is greater than or equal to one-half of a diameter D3 of the screw rod; characterized in that the second chip flute width D2 of each second chip flute is tapered off toward the screw thread section, and a difference between the second chip flute width D2 of each second chip flute adjacent to the drill bit section and the second chip flute width D2 of each second chip flute adjacent to the screw thread section is within 0.5 mm.