A feeding and reversing mechanism for a strapping machine, comprising: A base including an installation wall provided with a pivot thereon; a forward-reverse wheel assembly mounted on the installation wall and including an active wheel and a passive wheel adjacent to the active wheel for feeding and reversing a strapping band passing between the active wheel and the passive wheel; a tension wheel assembly including a tension active wheel mounted on the installation wall and a tension passive wheel adjacent to the tension active wheel, wherein the tension passive wheel is movable relative to the tension active wheel; a first arm including spaced first and second ends (51, 54); a second arm including spaced first and second ends (551, 553), with a rotary member mounted to the second end of the second arm and being in contact with a cam; a first spring unit including a spring and a fixing piece, with the first spring unit mounted on the first arm by extending the fixing piece through the spring and the first arm, with the spring biasing the first arm so that a gap is provided between the tension passive wheel and the tension active wheel for the strapping band to pass through; and a second spring unit including a tension spring and a fastener, with the second spring unit installed on the first and second arms (50, 55) by extending the fastener through the tension spring, the first arm, and the second arm, with the second arm being pivoted to move the tension passive wheel toward the tension active wheel to clamp the strapping band securely when the cam rotates; characterized in that the first end of the first arm is mounted around the pivot and is pivotable about an axis defined by the pivot, with the tension passive wheel mounted on the second end of the first arm, wherein the first end of the second arm is mounted around the pivot and is pivotable about the axis defined by the pivot. A base including an installation wall provided with a pivot thereon; a forward-reverse wheel assembly mounted on the installation wall and including an active wheel and a passive wheel adjacent to the active wheel for feeding and reversing a strapping band passing between the active wheel and the passive wheel; a tension wheel assembly including a tension active wheel mounted on the installation wall and a tension passive wheel adjacent to the tension active wheel, wherein the tension passive wheel is movable relative to the tension active wheel; a first arm including spaced first and second ends (51, 54); a second arm including spaced first and second ends (551, 553), with a rotary member mounted to the second end of the second arm and being in contact with a cam; a first spring unit including a spring and a fixing piece, with the first spring unit mounted on the first arm by extending the fixing piece through the spring and the first arm, with the spring biasing the first arm so that a gap is provided between the tension passive wheel and the tension active wheel for the strapping band to pass through; and a second spring unit including a tension spring and a fastener, with the second spring unit installed on the first and second arms (50, 55) by extending the fastener through the tension spring, the first arm, and the second arm, with the second arm being pivoted to move the tension passive wheel toward the tension active wheel to clamp the strapping band securely when the cam rotates; characterized in that the first end of the first arm is mounted around the pivot and is pivotable about an axis defined by the pivot, with the tension passive wheel mounted on the second end of the first arm, wherein the first end of the second arm is mounted around the pivot and is pivotable about the axis defined by the pivot.