In this paper,in order to realize the high-resolution spectral measu rement of low light,we propose a new spectral measurement method which is based on a digital micro-mirror device (DMD) and a photoelectric multiplier tube (PMT).Firstly,the spectrum of the measured light is imaged on a DMD by the dispersive optics system based on a small-size slit.Secondly,by the rotation of the micro-mirr ors of the DMD per column,the spectrum is reflected to a PMT according to the different wavelengths.Lastly,t he measurement of the spectrum is achieved through the scanning mode.The contrast experiments of our method and a charge-coupled device (CCD) spectrometer are performed,and the experiments for different low light con ditions are also performed.At last,the signal-to-noise ratio (SNR) experiment of the system is conducted.The results show that the spectral resolution is 0.23nm,the sensitivity of the spectral system is less than 4.6pW,and the SNR performance is also perfect.Co mpared with the conventional spectroscopy technique,t his spectral measurement method has the merits of low price,easy implementation and stable performance.