To avoid the inconvenience and danger caused by using air or oxygen as a regenerating gas for coked catalysts, this work proposes an effective regeneration method for the fouled Al-promoted sulfated zirconia (AL/SZ) catalyst. This work tries hydrogen for regenerating fouled catalysts; nevertheless, regaining activity is low when introducing atmospheric hydrogen as a regenerating gas. Fortunately, over 98% of original activity can be regained using high pressure hydrogen (2.1 MPa) at 250 degrees C within 8 h. The operation temperature for this new regeneration method is much lower than that for conventional methods using air or oxygen as a regenerating gas. This method does not affect the product distribution of n-C4 isomerization.