Objetive: A double detectors near infrared (NIR) diffuse spectrometer is introduced in order to improve the stability of the spectral signal. Method :The characteristic of the spectrometer is that the monochromatic beam is separated into two beams light by a splitter. One detector collects the radiation of one beam light directly. Another beam light irradiates the sample’s surface after pass through an integrating sphere. The diffuse light of sample is collected by another detector on the integrating sphere. The value of the two detectors is compared and the absorbency is computed. Result:The instrument is used to detect the diffuse reflectivity of standard diffuse reflectance surface. The mean correlation coefficient is 0.995 between the measure diffuse reflectance and the real values. The mean standard deviation is 0.01. In addition the instrument is used to measure some components of milk powder

milk and soy sauce. The correlation coefficients of calibration are over 0.8. Conclusion: It account for that the homemade spectrometer can get the right diffuse reflectivity. And food component analysis can be done with the instrument.