Achieving nonblockingness in supervisory control imposes a major challenge when the number of states of a target system is large, often owing to synchronous product of many relatively small local components. To overcome this difficulty, in this paper we first present a distributed supervisory control problem, then provide an aggregative synthesis approach that computes nonblocking distributed supervisors. The key to the success of this approach is a newly developed automaton abstraction technique, that removes irrelevant internal transitions at each synthesis stage so that nonblocking supervisor synthesis can be carried out on relatively small abstracted models.