Optical sensing methods have appeared as potential alternatives for quick, non-invasive, and label-free evaluation of milk quality. In this paper aims to examine the performance nondestructive method using the optical sensing techniques for milk adulteration using spectrometer. There are two setup experiments which are using probe and cuvette. The experiment setup involves the use of a UV–VIS-NIR spectrometer, Halogen light source and a probe or cuvette for initial setup. The experiment starts by mixing urea solution as adulterant from 500–2500 ppm with milk. The solution will mix well, and the experiment is performed under room temperature. The effect of urea concentration in milk is observed using spectra suite software for examined the absorbance spectral peak. Based on the result, the linearity of optical sensor is more than 95% for probe and 97% for cuvette is observed with limit of detection less than 300 ppm. By examining using cuvette gives 20% sensitivity improvement compared to probe for each sample. In the end of this paper, this non-destructive method using optical sensor is the simplest, ease and practical method in accessing milk protein, fat and adulteration.