Chitinous materials are important sources for many bio-medical applications; and the process monitoring is a key factor for better quality control of chitosan production. In this study, chitin and chitosan in suspension form were analyzed using near infrared (NIR) spectroscopy. Two models including multiple linear regression (MLR) and modified partial least square regression (MPLSR) were adopted for studying the degree of deacetylation (DD) of chitinous materials in order to assure a better quality monitoring and control for chitosan production. During the process of the deacetylation, the real-time measurements of suspension were conducted. The MPLSR model with second derivative spectra in the range of 600-1000 and 1400-1500 nm yielded the best results, which were rc = 0.991, SEC = 0.019, RESC = 1.4%, rp = 0.990, SEP = 0.022, RSEP = 3.4%, RPD = 9.4. The NIR measurements of DD status of chitinous suspension could be achieved by using either MLR or MPLSR model developed in this study. It provides great application potentials to the real-time and on-line inspection for the quality monitoring and control of the chitosan production during deacetylation process.