Considering multiple potential suppliers with supply risk and private cost information，this paper studies the optimal design of dual-sourcing auctions where the suppliers bid the wholesale prices． Firstly， under a general buyer revenue function，the optimal allocation rule and suppliers’bidding equilibrium are de-rived，and the results are compared with the single-sourcing case and the symmetric information case，respec-tively． Comparisons show that both the buyer and suppliers gain more expected profits than under the optimal single-sourcing mechanism，and information asymmetry benefits suppliers but hurts the buyer and the entire supply chain． Then，in a newsvendor setting and a monopoly setting，the paper further analyzes the diversifica-tion degree of quantity allocation，the effects of information asymmetry，and the value of the dual-sourcing op-tion． Ｒesults show that the diversification degree of quantity allocation increases with the supply risk and the homogeneity level of winners’profit-margin contributions to the buyer． The higher-cost winner charges a higher per unit information rent than the lower-cost winner does，which results in a lower diversification degree as compared with the symmetric information case． Moreover，when the supply risk or the number of bidders in-creases，the value of the dual-sourcing option increases．