In this article, a transaction cost approach is adopted to analyze the two e-government outsourcing ways，BOO and BOT, and the model of e-government benefit and profits of the vendor is constructed. The contract term, public benefit, the maximum benefits and maximum profits of the vendor of the two outsourcing models are discussed respectively.Then based on the relational expression of expected benefit of e-government and risk of vendor's decreasing of e-government quality,the incentive mechanism of each is put forward to achieve the multi-win of the public, vendor and government department. A case example is given in the end.