In order to realize the intelligent grain preparation of fermented grains in the process of liquor production,an online near infrared(NIR) spectroscopy system was developed in this paper for the real time detection of the water,starch and acid contents of fermented grains.The online signal was converted as 4-20 mA current for the intelligent allocation of grains in the process of Chinese liquor brewing.This real time detection system was carried out at liuchixiang Chinese liquor brewing plant in Yibin,Sichuan province.The average errors for Lab NIR analysis of water,starch,acid in fermented grains were -0.25%,0.38% and 0.29 mmol/10 g,while the standard errors of prediction(SEP) of water,starch and acid were 0.60%,0.75% and 0.18 mmol/10 g,respectively.The average errors for online NIR quantitative analysis of water,starch,acid in fermented grains were -0.75%,0.48% and 0.29 mmol/10 g,while the SEP of water,starch and acid were 0.66%,0.97%and 0.22 mmol/10 g,respectively.Compared with the results of Lab NIR analysis,the average errors and standard deviations of this online analysis were amplified,but the precision of online NIR analysis could be qualified for grains addition in the automation of the whole production line.