Spectroradiometer is a tool to measure both the wavelength and amplitude of the light emitted from a light source. This light measurement identifies wavelengths based on where the light hits the detector array, allowing the entire spectrum to be captured in a single acquisition. How to identify and use a spectrometer correctly so that the acquired wavelength data can form a spectral library. There are many types of spectroradiometers, but it must be ensured that the reflected wavelengths recorded fall within a certain range. This determines which spectroradiometer should be used. In addition, we also need to know which object will be recorded if its reflectivity. With a known wavelength range, the type of spectrometer can be determined. It is also important to consider the measurement step associated with the existence of the observed object. If measurements have been obtained, the results can be used to construct a spectral library representing each agreed end-member. The spectrum library is a very important reference in processing remote sensing data. In this study, a portable spectrometer was used with a wavelength range of 0.450 to 0.800 micrometers. Subjects recorded included leaves of rice plants in healthy plant conditions.