Abstract: Standard white field meter is the key equipment in the field of display measurement, and its measurement performance directly affects the accuracy of color, brightness and uniformity calibration of the display. This paper aims to improve the measurability of standard white field instrument. Through the measurability design, this paper analyzes the typical metrological scenarios, identifies metrological stakeholders, and captures, classifies, organizes and analyzes the needs of stakeholders. The key parameter of relative spectral radiance is found, and the measurability design scheme of this parameter is given. Finally, the effectiveness of the design scheme is verified by experiments. Taking relative spectral radiance into account can improve the accuracy of chromaticity coordinates and related color temperature measurements, provide more reliable quantification traceability for color analyzers, and help improve the quality of display products and user experience. The research results can provide reference for the design of the metrology of display measuring instruments.