A fan impeller structure includes an annular body. The annular body has a top section and a receiving space. At least one first bending section is formed between the top section and the annular body. At least one recess is formed at the first bending section. At least one flow guide hole is formed between the first bending section and the recess in communication with the receiving space. In operation, the airflow conducted into the receiving space is increased. Moreover, no matter whether the fan impeller structure is clockwise rotated or counterclockwise rotated, the airflow can be conducted into the receiving space through the flow guide hole. Accordingly, the heat dissipation effect will not be affected by the rotational direction of the fan impeller structure.