The invention provides a case structure of an outer rotor motor, which comprises an annular outer side wall (1) and an end cover (2), wherein the end cover (2) is positioned at the bottom end of the outer side wall (1), a cavity (3) is formed in the middle of the case structure, the top of the case structure is open for forming an opening (4), a connection seat (5) is formed in the center of the end cover (2), the center of the connection seat (5) is provided with a key groove (7) connected with a transmission shaft of the motor, the connection seat (5) and the annular outer side wall (1) areconnected through a plurality of blades (8), and air inlet openings (9) are formed between two adjacent blades (8). The case structure is provided with a plurality of blades, the air inlet openings are formed between the two adjacent blades, when the case rotates, the blades generate the air flow blowing in the axial direction for forming the heat radiation on a motor winding, and the heat radiation effect is good. The blades can generate the air flow blowing both in positive rotation or reverse rotation, and the heat radiation on the motor winding can be formed. The injection molding case structure has the certain buffer effect, and the vibration can be reduced.