Standard JJG 512-2021 specifies the specification for calibrating optoelectronic integral blue light whiteness meters. This standard applies to newly manufactured, neutralized and repaired whiteness meters, including first verification, subsequent verification and inspection in use. The whiteness meter is composed of components such as Light source, Optical inspection system, detection system and data processing display system. It is usually equipped with blackbody and working whiteboard for zero point and whiteness calibration. Measurement principles are based on sample Reflection spectrum characteristics, with special attention to the determination of blue light whiteness, that is, the measurement result at the effective peak wavelength at 457nm. This standard does not apply to the verification of fluorescence whiteness meters or their fluorescence measurement results. Reference documents include relevant photometers, standard swatches and color difference meters. Accuracy and Reliability of whiteness meters in industrial production and quality control are ensured through the implementation of this standard. Accuracy and Stability in whiteness measurement are guaranteed.