Legal analysis: not illegal. There is no difference between stamping before signing and stamping after signing. Whether to seal or sign first has no substantial influence on the validity of the contract. As long as it is the true intention of both parties, the content is legal and valid and does not violate existing laws and regulations.

Legal basis: Article 490 of the Civil Code of People's Republic of China (PRC). If the parties enter into a contract in the form of a contract, the contract shall be established when the parties sign, seal or press their fingerprints. Before signing, sealing or fingerprinting, one party has fulfilled its main obligations, and the contract is established when the other party accepts it.

A contract shall be concluded in written form as stipulated by laws, administrative regulations or agreed by the parties. If the parties do not do this in writing, but one party has fulfilled its main obligations and the other party accepts it, the contract is established.