本文对招投标行为的性质、政府采购合同成立的时间以及拒签政府采购合同的责任等问题进行了分析,认为招标行为是要约邀请,投标行为是要约;政府采购合同自双方在合同上签字或盖章时成立;采购人拒发中标通知书或已发中标通知书但拒绝与中标的供应商签订合同,采购人承担的是缔约过失责任,但不应承担行政责任。中标的供应商拒绝与采购人签订合同,应承担缔约过失责任和行政责任。 This paper analyzes the nature of the bidding behavior, the time of establishment of the government procurement contract and the responsibility of refusing to sign the government procurement contract. It considers that the bidding is an invitation to offer and the bidding is an offer. The government procurement contract is signed or contract signed by both parties Zhang Shi established; the purchaser refused to sign the successful bidder or notice of the successful bidder but refused to bid with the successful supplier of the contract, the purchaser assumes the contracting fault liability, but should not assume administrative responsibility. The successful supplier refuses to sign the contract with the purchaser, and shall bear the fault liability and the administrative liability of the contracting party.