A full pneumatic differential slip shaft which is formed by a differential slip ring unit sleeved on a core shaft mainly comprises a differential slip ring and a gas damping ring, wherein the differential slip ring is provided with a first ring, a second ring, and a plurality of ejection holding components, wherein the first ring and the second ring are sleeved together, and the ejection holding components are disposed between the first ring and the second ring, the gas damping ring is provided with a gas filled ring for guiding gas pressure in, and a pneumatic component which is in frictional contact with the second ring is affected by the gas pressure in the gas filled ring. Therefore, the full pneumatic component is driven by predetermined gas pressure to push the second ring to further press the ejection holding components, then the ejection holding components extend out of the first ring to achieve the purpose of clamping a pipe, and thereby the utility model has certain actions and can increase stability of clamping.