Threshold concentration (Smin)is termed the minimum substrate concentration of biodegradation oforganic pollutants，which is significant in the removal of trace organic compounds for these compounds can not beeliminated from environment effectively by traditional biological techniques. But the value of Smin is not constant,and is influenced by many factors，such as the characteristic of organic matter，species of microorganism,environment condition and biodegradation pathway. Several factors influencing Smin were studied in this paper,including substrate concentration，organism culture mode，and additional carbon source. The results indicated thatthe lower the substrate concentration is，the lower the Smin value is，and vice versa. The Smin value of continuousculture is lower than that of batch culture，and the former is more suitable to enrich organism degrading traceorganic compounds. The else carbon source (glucose)weakens the affinity of ceils for catabolic objectivecompounds，which is disadvantage to reach lower Smin value.