Legal analysis: It depends on the situation. If the party authorizes another person to sign on his behalf or ratifies it later, his signing act is legal and useful; if there is no legal authorization from the party concerned, the signing act is invalid.

Legal basis: "The People's Republic of China and the Civil Code"

Article 161 A civil subject may perform civil legal acts through an agent.

According to legal provisions, agreement between the parties or the nature of the civil legal act, civil legal acts that should be carried out by the person himself shall not be represented by an agent.

Article 162: Civil legal acts performed by an agent in the name of the principal within the scope of agency authority shall be effective against the principal.

Article 163: Agency includes principal agent and legal agent.

The authorized agent shall exercise the power of agency in accordance with the principal's entrustment. The legal agent shall exercise the power of agency in accordance with the provisions of the law.

Article 164 If the agent fails to perform or does not fully perform his duties and causes damage to the principal, he shall bear civil liability.

If the agent and the counterparty collude maliciously and harm the legitimate rights and interests of the principal, the agent and the counterparty shall bear joint and several liability.