Abstract: In 2018, there will be a major revision of the International System of Units (SI) which will result in all of the seven base units being defined or reworded by fixing the values of certain atomic or fundamental constants. The future of vacuum metrology will rely on quantum-based primary standard based on optical methods which represents a disruptive change in the way of realizing and disseminating the SI unit of pressure, the pascal. Compared to conventional standards, these new quantum-based vacuum primary standards will potentially enable zero-chain SI traceability, fast response time, high accuracy and unrestricted circumstance. The research and development of quantum-based primary vacuum standard launched by NIST, PTB and SNTRI in the field of vacuum metrology are reviewed. The paper reviews the theoretical and experimental foundations and key technologies of three methods, including refractive index method, absorption method and
rate of cold atom loss method.

Key words: Quantum vacuum standard, Refractive index, Fabry-Perot cavity, Absorption spectrum, Cold atom, Magneto-optical trap