It's not illegal to sign someone else's name. If authorized by me, the proxy signature is valid for me, and I shall bear the consequences of the legal relationship confirmed by the signature. Without my authorization, the proxy signing is invalid, and the person who has no right to proxy signing shall bear the legal responsibility of proxy signing. Article 169 of the Civil Code stipulates that if an agent needs to entrust a third party, he shall obtain the consent or ratification of the principal. If the entrusted agent is approved or ratified by the principal, the principal may directly instruct the entrusted third party on the agency affairs, and the agent is only responsible for the choice and instruction of the third party. If the entrusted agent is not approved or ratified by the principal, the agent shall be responsible for the behavior of the entrusted third party; However, in an emergency, in order to safeguard the interests of the principal, the agent needs to entrust a third party.