This article discusses the diachronic development of the Chinese long passive. The diachronic analysis is built on structural analysis of the long passive and the wei … suo passive. I show that both constructions involve a highly restricted embedded clause (a vP) and that both are derived via Aʹ-movement. Based on their structural parallelism, I argue that the wei … suo passive, which first appeared in Late Archaic Chinese (fifth century bce ~ third century bce), is the direct ancestor of the long passive. The long passive inherits its Aʹ properties and biclausal structure from the wei … suo passive. I also show that the diachronic development from the wei … suo passive to the long passive took place in two steps: (i) the loss of suo following a morphophonological change in Early Middle Chinese (second century bce ~ second century ce, and (ii) the replacement of wei by bei in Middle Chinese (third century ce ~ sixth century ce).