中华人民共和国劳动合同法 第十条

建立劳动关系，应当订立书面劳动合同。
已建立劳动关系，未同时订立书面劳动合同的，应当自用工之日起一个月内订立书面劳动合同。
用人单位与劳动者在用工前订立劳动合同的，劳动关系自用工之日起建立。

Labor Contract Law of the People’s Republic of China, Article 10

To establish a labor relationship, a written labor contract shall be concluded.

In the event that no written labor contract is concluded at the time when a labor relationship is established, such a contract shall be concluded within one month as of the date when the employing unit employs a worker.

Where an employing unit and a worker conclude a labor contract before the latter starts to work, the labor relationship shall be established as of the date when the latter starts to work.