An air compressor having a pressure gauge, the pressure gauge comprising: a hollow tube which is transparent and is formed in a cylinder shape, and the hollow tube including an accommodation chamber, a connector fixed on an outer side of a first distal segment of the hollow tube and having a conduit which communicates with the accommodation chamber of the hollow tube, a display unit mounted on an outer wall of the hollow tube adjacent to the first distal segment and having at least one scale graduation to indicate a pressure value of the air compressor; a drive element including a protection unit and being accommodated in the hollow tube so as to move linearly after being pushed by compressed airs of the air compressor, such that the pressure value is indicated by using a length of movement of the drive element, the drive element including a first open segment formed on a first end of the drive element, a second distal segment formed on a second end of the drive element, a receiving portion defined in the drive element, a hollow extension extending out of the first open segment from a center of a bottom of the receiving portion of the second distal segment; a resilient element received in the receiving portion of the drive element and fitted on the hollow extension; a cap including a seat extending from a center of an interior of the cap, wherein a push bolt extends from a top of the seat and multiple passages are defined on an outer wall of the cap, wherein an end of the resilient element contacts with the cap; characterized in that the connector is fixed on a center of the outer side of said first distal segment of the hollow tube; a protrusion is formed on an inner wall of the hollow extension of the drive element, said protrusion having an air channel; wherein an anti-leak spring is received in the hollow extension of the drive element, wherein a first end of the anti-leak spring abuts against the protrusion and a second end of the anti-leak spring contacts with the protection unit; and the push bolt being formed in a cross-shaped column shape. a hollow tube which is transparent and is formed in a cylinder shape, and the hollow tube including an accommodation chamber, a connector fixed on an outer side of a first distal segment of the hollow tube and having a conduit which communicates with the accommodation chamber of the hollow tube, a display unit mounted on an outer wall of the hollow tube adjacent to the first distal segment and having at least one scale graduation to indicate a pressure value of the air compressor; a drive element including a protection unit and being accommodated in the hollow tube so as to move linearly after being pushed by compressed airs of the air compressor, such that the pressure value is indicated by using a length of movement of the drive element, the drive element including a first open segment formed on a first end of the drive element, a second distal segment formed on a second end of the drive element, a receiving portion defined in the drive element, a hollow extension extending out of the first open segment from a center of a bottom of the receiving portion of the second distal segment; a resilient element received in the receiving portion of the drive element and fitted on the hollow extension; a cap including a seat extending from a center of an interior of the cap, wherein a push bolt extends from a top of the seat and multiple passages are defined on an outer wall of the cap, wherein an end of the resilient element contacts with the cap; characterized in that the connector is fixed on a center of the outer side of said first distal segment of the hollow tube; a protrusion is formed on an inner wall of the hollow extension of the drive element, said protrusion having an air channel; wherein an anti-leak spring is received in the hollow extension of the drive element, wherein a first end of the anti-leak spring abuts against the protrusion and a second end of the anti-leak spring contacts with the protection unit; and the push bolt being formed in a cross-shaped column shape.