Many consider Augustus to be Rome's greatest emperor; his policies certainly extended the Empire's life span and initiated the celebrated Pax Romana or Pax Augusta. He was intelligent,decisive，and a shrewd politician, but he was not perhaps as charismatic as Julius Caesar, Nevertheless, his legacy proved more enduring.
The longevity of Augustus' reign and its legacy to the Roman world should not be overlooked as a key factor in its success. As Tacitus wrote, the younger generations alive in AD 14 had never known any form of government other than the Principate. Had Augustus died earlier (in 23 BC,for instance), matters might have turned out differently. The attrition of the civil wars on the old Republican oligarchy and the longevity of Augustus, therefore, must be seen as major contributing factors in the transformation of the Roman state into a monarchy in these years.
Augustus' own experience, his patience, his tact, and his political acumen also played their parts. He directed the future of the Empire down many lasting paths, from the existence of a standing professional army stationed at or near the frontiers, to the dynastic principle so often employed in the imperial succession, to the embellishment of the capital at the emperor's expense. Augustus' ultimate legacy was the peace and prosperity the Empire enjoyed for the next two centuries under the system he initiated.
His memory was enshrined in the political ethos of the Imperial age as a paradigm of the good emperor. Every emperor of Rome adopted his name, Caesar Augustus, which gradually lost its character as a name and eventually became a title.