A sinus dental implant for implanting into an alveolar hole on a patient's upper gum , comprising: a main body having two opposite ends defined as a drilling end and a connection end , and an embedment peripheral surface extended from the drilling end toward the connection end ; and the drilling end having an outer peripheral area formed into a drilling zone capable of contacting with a bottom of the alveolar hole and a sunken central area formed into a recess surrounded by the drilling zone ; an external thread being formed on the embedment peripheral surface of the main body to extend in a first spiral direction (D1) for engaging with a side wall surface of the alveolar hole ; and a plurality of spiral cutting flutes being formed on the main body and the external thread to extend from the drilling zone toward the connection end in a second spiral direction (D2), which is opposite to the first spiral direction (D1), and a cut being formed between every spiral cutting flute and the recess for communicating the spiral cutting flute with the recess ; wherein the drilling zone is divided by the spiral cutting flutes into a plurality of drilling segments that are circumferentially spaced along the recess ; the sinus dental implant being characterized in that every drilling segment has a lowest portion defined as a lower drilling portion , the drilling segment rises gradually from the lower drilling portion of the drilling segment toward one of the spiral cutting flutes to form an upper drilling portion , so that a guide surface is formed between the lower drilling portion and the upper drilling portion while a guide space is also formed between the lower drilling portion and the upper drilling portion to communicate with the recess and the spiral cutting flute . a main body having two opposite ends defined as a drilling end and a connection end , and an embedment peripheral surface extended from the drilling end toward the connection end ; and the drilling end having an outer peripheral area formed into a drilling zone capable of contacting with a bottom of the alveolar hole and a sunken central area formed into a recess surrounded by the drilling zone ; an external thread being formed on the embedment peripheral surface of the main body to extend in a first spiral direction (D1) for engaging with a side wall surface of the alveolar hole ; and a plurality of spiral cutting flutes being formed on the main body and the external thread to extend from the drilling zone toward the connection end in a second spiral direction (D2), which is opposite to the first spiral direction (D1), and a cut being formed between every spiral cutting flute and the recess for communicating the spiral cutting flute with the recess ; wherein the drilling zone is divided by the spiral cutting flutes into a plurality of drilling segments that are circumferentially spaced along the recess ; the sinus dental implant being characterized in that every drilling segment has a lowest portion defined as a lower drilling portion , the drilling segment rises gradually from the lower drilling portion of the drilling segment toward one of the spiral cutting flutes to form an upper drilling portion , so that a guide surface is formed between the lower drilling portion and the upper drilling portion while a guide space is also formed between the lower drilling portion and the upper drilling portion to communicate with the recess and the spiral cutting flute . <EOS>