Bioreaction Online Detection System (BODS) is an instrument for fully automatic on-line sampling, processing, detection and sample retention of bioreactors. The instrument has the characteristics of small sampling volume, multi-parameter detection, full automation and high effectiveness, which can avoid the impact of too much sampling volume on the whole fermentation system. At the same time, multi-parameter detection can display the biomass, substrate consumption and product generation in the tank in real time, and can also adjust the feedback control system in time to realize the accurate control of substrate feeding, so as to improve the control efficiency of the fermentation process. It provides data support for fermentation process optimization and process amplification.