A mechanism to implement the efficient allocation of pollution was designed in this paper， and it shows that even the payoff information of the factories is private， the factories would tell the truth about their payoff information only if they are rational， by which the efficient allocation of pollution is realized. To play its role the mechanism does not need a game environment-complete rationality of factories is common knowledge， which means the mechanism is of great practicality. The research results show that as long as the factories are rational and the allocators of pollution are allowed to charge the factories， we can implement the efficient allo- cation of pollution by mechanism design.