Online auction and multi-object auction are the research background of this paper.In the paper,a bidder's dominant offer and an auctioneer's expected revenue are analyzed and compared in a special sequential auction of two heterogeneous objects,in which the auctioneer's information are hidden,partial hidden or revealed step by step.The impact of information advantage on valuation and efficiency in auctions is analyzed.Some valuable conclusions are drawn about the information strategy and mechani...