A photo sensor, a manufacturing method thereof, and a display panel are disclosed. By an ion implantation method forming an N-type region and a P-type region on a surface of polycrystalline silicon in a same layer respectively, compatibility with an ion implantation process is ensured, while covering a layer of an amorphous silicon photosensitive layer on the polycrystalline silicon enhances light absorption ability and can increase photo-generated electron-hole pairs. Furthermore, built-in electric fields exist on a horizontal direction and a vertical direction, which can more effectively separate the electron-hole pairs to enhance photo-generated electric current to improve accuracy of fingerprint recognition.