1, valid. The contract is legally binding only if it is sealed by both parties, but not signed by both parties. If the signature or seal of the contract meets any of these conditions, the contract is valid. If the contract is neither signed nor sealed, but one party has fulfilled its contractual obligations and the other party has accepted it, then the contract is also valid;

2. Legal basis: Article 490th 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.

Second, under what circumstances can't the contract be established?

1. During the performance of the contract, the other party refused to accept the performance. Even if the other party fulfills its main obligations, the contract cannot be effectively established, because it means that both parties have not reached an agreement on the contents of the contract;

2. If one party performs the secondary obligation and the other party accepts it, but the debtor refuses to perform the primary obligation, the other party cannot request the debtor to continue to perform the primary obligation, that is, the contract is not established.