GB/T 4340.3-2025 "Metal materials, Vickers Hardness test, Part 3: Calibration of standard Hardness blocks" is a national standard, to be implemented in 2025, applicable to the calibration and quality control of Vickers Hardness standard blocks. The standard specifies in detail the calibration method, technical requirements and uncertainty assessment of standard Hardness blocks, covering key indicators such as Hardness uniformity, Stability, indentation Measurement accuracy. The standard clarifies the calibration procedure, environmental conditions, equipment and data processing requirements, and introduces digitalization measurement technology to improve the calibration accuracy. Compared with the old version, the uncertainty calculation method is optimized, and the evaluation requirements for the surface mass and long-term stability of the standard block are added.