Legal analysis: the contract is established when both parties sign or seal it. As can be seen from this clause, the parties conclude a contract in writing, as long as they have one of the elements of signature and seal, the contract is established, and it is not required to have both elements at the same time. However, in lawyer's practice, it often happens that the parties agree to sign and seal as the effective condition of the contract. Based on the principle of autonomy of will, the law recognizes the effective conditions agreed by the parties.

Legal basis: Article 469 of the Civil Code of People's Republic of China (PRC), the parties may conclude a contract in written form, orally or in other forms. Written form refers to contracts, letters, telegrams, telexes, faxes and other forms that can tangibly express the contents contained. A data message that can tangibly express its content through electronic data interchange, e-mail, etc. , and can be retrieved at any time, are considered in writing.