Two problems often appear in estate auction.The first is to whom the buyer can claim cancellation of the contract,if he can't get the estate.The second is whether the tenant can still claim his priority to the estate.In auction,we can't use the principle of agency,fiduciary and mediation to explain the relations among client,auctioneer and buyer,because it doesn't accord with the auction practices and the Action Law section 40.The undisclosed agency in Contract Law may be an adapt explanation to the relations.According to the law hermeneutic,we should narrow the scopes of the tenant priority and exclude it from auction.