In this study, a lab-on-chip (LOC) system is designed for the cell sensors to provide a high-efficient continuous analysis platform of acute toxicants in water environment. The chip is composed of three domains, including counter-flow micromixers, a T-junction droplet generator and time delay channels (TD-Cs). Water sample and bioluminescent bacterium Vibrio Fischeri (VF) are imported into the micromixers before that the droplet generator encapsulates them inside aqueous droplets separated by air. Air flow is the disperse medium, which can guarantee sufficient oxygen supply for the cells in droplets. The system shows high reliability and stability through numerical and experimental investigations.