The present disclosure discloses a quantum dot and a preparation method thereof, the method comprises a plurality of following steps: preparing a quantum dot solution; preparing an ion-containing organic ligand precursor; adding the ion-containing organic ligand precursor into the quantum dot solution, and making a surface-modification to the quantum dots, before obtaining the quantum dots having the surfaces modified; or providing a quantum dot solution; providing an ion-containing organic ligand precursor; mixing the ion-containing organic ligand precursor and the quantum dot solution, to make a ligand exchanging, before centrifuging and obtaining the quantum dots having the ligand exchanged.