In order to develop a real-time measuring instrument based on NIR spectral absorption method for forest surface litter moisture content, the relationship between water content and absorption spectrum of litter in forest was analyzed in this paper. In addition, four kinds of forest surface litter were selected and the infrared absorption spectrum measuring device was constructed. Besides, the infrared absorption spectrum corresponding to different water content were obtained. The relationship between the different moisture content and the peak absorption intensity, the absorption valley areaand the vertical axis of the valley connection and the valley connection are analyzed. The results showed that the peak value of water absorption was near 1 450 nm, and the correlation between water content and peak absorption intensity of forest litter was better. The single regression equation was well tested by F-test, and the relative uncertainty of slope was less than 1.0% and the intercept of the relative uncertainty of less than 0.51%, the correlation coefficient r>0.95. It provides the basis for the light source and calibration process of the moisture content real-time measuring instrument.