Legal analysis: the contract is valid without the official seal of the unit but signed by the legal representative. The legal representative shall exercise authority on behalf of the legal person, and the legal person shall be responsible for the acts carried out in the name of the legal person. The official seal is not a necessary condition for the validity of the contract.

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.