Abstract: The effects of acute progressive hypoxia on the respiration rate of the Chinese freshwater crab,Eriocheir sinensis,acclimated at three temperatures were investigated with a closed respirometer.E.sinensis can maintain its respiration rate down to the critical point (Pc) and from this point its respiration rate declines rapidly,reaching zero at a lower ambient oxygen concentration called the zero respiration oxygen concentration.Because of this,a new hyperbolic equation is introduced to express the relationship between respiration rate and ambient oxygen concentration.A new method for calculating the Pc value is also developed.The Pc values for E.sinensis at 20-35℃ range from 1.92-3.47 mg/l.