Abstract: A novel photodiode structure, a preparation method and a circuit structure are provided. The novel photodiode structure includes a substrate having a first doping type, a functional doping area having a second doping type, a surface doping area having the first doping type, and an auxiliary doping area having the second doping type. By forming a non-uniformly doped functional doping area, the present disclosure forms a self-built potential difference in the functional doping area and drives the moving direction of the photogenerated carriers. The photogenerated carriers may be accelerated by the potential difference, so that the collected carriers will directly enter the subsequent circuit through the transport gate. In addition, the loop shape of the auxiliary doping area can increase the area of receiving charges, in a result, the auxiliary doping area can receive the transported carriers faster, thereby further enhancing the transport efficiency of the photogenerated carriers.