After winning the bid for a construction project, the bid inviter and the winning bidder shall, within 30 days from the date of issuing the letter of acceptance, conclude a written contract in accordance with the bidding documents and the bid documents of the winning bidder.
 1、 The following engineering construction projects within the territory of the People's Republic of China, including project survey, design, construction, supervision and procurement of important equipment and materials related to engineering construction, must be subject to bidding:
 （1） Large infrastructure, public utilities and other projects related to social public interests and public safety;
 （2） Projects wholly or partly invested with state-owned funds or financed by the state;
 （3） Projects using loans and aid funds from international organizations or foreign governments.
 2、 The bid of the winning bidder shall meet one of the following conditions:
 （1） Be able to meet various comprehensive evaluation standards specified in the bidding documents to the maximum extent;
 （2） It can meet the substantive requirements of the bidding documents, and the evaluated bid price is the lowest; Except that the bid price is lower than the cost.
 [Legal Basis]
 According to Article 46 of the Law of the People's Republic of China on Tenders and Bids, the tenderer and the winning bidder shall, within 30 days from the date of issuing the notification of award, conclude a written contract in accordance with the tender documents and the bid documents of the winning bidder. The tenderer and the winning bidder may not enter into any other agreement that deviates from the substantive contents of the contract.
 If the bid invitation documents require the winning bidder to submit a performance security, the winning bidder shall do so.