An air compressor with a connection structure for a motor, comprising: a base including multiple positioning orifices which are a first positioning orifice and a second positioning orifice; a cylinder connected on the base and including an air storage seat; a motor fixed on the base, a small-diameter gear being inserted through the first positioning orifice of the base to fit on a central shaft of the motor, a bearing housing of the motor being accommodated in the first positioning orifice, and a transmission mechanism actuating a piston to move in the cylinder reciprocately so as to compress air; characterized in that: the motor includes a magnetic coil made of metal and provided on an external surface of the motor, wherein the magnetic coil is configured to guide magnetism so as to enhance operating efficiency of the motor; wherein the magnetic coil of the motor includes a first segment and a second segment; the base includes two symmetrical elongated plates extending from a rear end of the base, and the two symmetrical elongated plates have two hooks extending therefrom respectively, the base further includes two symmetrical arcuate retainers extending from two inner walls of the two symmetrical elongated plates individually; the first segment of the magnetic coil of the motor abuts against two top faces of the two symmetrical arcuate retainers, and the two hooks of the two symmetrical elongated plates of the base are engaged with the magnetic coil so that the motor is fixed on the base. a base including multiple positioning orifices which are a first positioning orifice and a second positioning orifice; a cylinder connected on the base and including an air storage seat; a motor fixed on the base, a small-diameter gear being inserted through the first positioning orifice of the base to fit on a central shaft of the motor, a bearing housing of the motor being accommodated in the first positioning orifice, and a transmission mechanism actuating a piston to move in the cylinder reciprocately so as to compress air; characterized in that: the motor includes a magnetic coil made of metal and provided on an external surface of the motor, wherein the magnetic coil is configured to guide magnetism so as to enhance operating efficiency of the motor; wherein the magnetic coil of the motor includes a first segment and a second segment; the base includes two symmetrical elongated plates extending from a rear end of the base, and the two symmetrical elongated plates have two hooks extending therefrom respectively, the base further includes two symmetrical arcuate retainers extending from two inner walls of the two symmetrical elongated plates individually; the first segment of the magnetic coil of the motor abuts against two top faces of the two symmetrical arcuate retainers, and the two hooks of the two symmetrical elongated plates of the base are engaged with the magnetic coil so that the motor is fixed on the base. the motor includes a magnetic coil made of metal and provided on an external surface of the motor, wherein the magnetic coil is configured to guide magnetism so as to enhance operating efficiency of the motor; wherein the magnetic coil of the motor includes a first segment and a second segment; the base includes two symmetrical elongated plates extending from a rear end of the base, and the two symmetrical elongated plates have two hooks extending therefrom respectively, the base further includes two symmetrical arcuate retainers extending from two inner walls of the two symmetrical elongated plates individually; the first segment of the magnetic coil of the motor abuts against two top faces of the two symmetrical arcuate retainers, and the two hooks of the two symmetrical elongated plates of the base are engaged with the magnetic coil so that the motor is fixed on the base.