The invention discloses a connecting structure for an oil filler cap. The connecting structure comprises an oil filler cap body (1) and an oil filler (3), wherein the oil filler cap body (1) comprises a fastening portion matched with the oil filler (3) and a cap (12) arranged on the fastening portion. Elastic clips (15) with inward and outward elastic amplitudes are arranged on the side face of the fastening portion, and screwing clamping blocks (31) opposite to the elastic clips (15) in position are arranged on the inner wall of the oil filler (3). A guiding groove (14) is formed in the side wall of the fastening portion, and the screwing clamping blocks (31) can be clamped in the guiding groove (14) which is a spirally-upward spiral groove. According to the connecting structure and connecting method for the oil filler cap, the structure is simple, the performance is stable, mounting and demounting are convenient, time and labor are saved, the machining cost is low, and a good sealing effect can be achieved.