The legal basis:
"Any entity or individual exploiting the patent of another shall conclude with the patentee a written license contract for exploitation and pay the patentee a fee for the exploitation of the patent. The licensee has no right to authorize any entity or individual, other than that referred to in the contract for exploitation, to exploit the patent." (Chinese Patent Law, Article 12)
"After the publication of the application for a patent for invention, the applicant may require the entity or individual exploiting the invention to pay an appropriate fee." (Chinese Patent Law, Article 13)
"Where any patent for invention, belonging to any state-owned enterprise or institution, is of great significance to the interest of the State or to the public interest, the competent departments concerned under the State Council and the people's governments of provinces, autonomous regions or municipalities directly under the Central Government may, after approval by the State Council, decide that the patented invention be spread and applied within the approved limits, and allow designated entities to exploit that invention. The exploiting entity shall, according to the regulations of the State, pay a fee for exploitation to the patentee. Any patent for invention belonging to a Chinese individual or an entity under collective ownership, which is of great significance to the interest of the State or to the public interest and is in need of spreading and application, may be treated alike by making reference to the provisions of the preceding paragraph." (Chinese Patent Law, Article 14)

Requirements:
1) Recordal Application Form
2) The counterpart of License Contract
3) Photography of Patent Certificate or Notice of Acceptance of Patent Application.
4) The Identity Certificate of Assignee and Assignor
5) Power of Attorney
6) Other required documents