Abstract: To promote the practical application of biological toxicity test, this paper introduces the research progress of biological toxicity test by using photogenic bacteria, algae, daphnia and fish as bio-monitors, and analyzes the advantages and disadvantages of the 4 indicating organisms used in biological toxicity test, and discovers the obvious difference of the indicators in detection range, detection time and detection limit. The research results show that due to the complex pollutants in practical condition, it is difficult to give an overall, efficient and objective assessment of pollutant toxicity with single bio-indicator, therefore it is necessary to carry out co-early-warning with the advantages of four bio-indicators for achieving the optimal effect. Based on the researches, we constructed a multi-biomonitor early-warning system. The test research on 17 typical pollutants in water sources area of Danjiangkou Reservoir shows the multi-bio-monitor early-warning system can improve alarming efficiency distinctly.