Abstract: The volume ratio of the emulsion before and after centrifugation is defined as centrifugal coefficient Vr,and the stability of the acrylamide and its derivatives inverse emulsion are evaluated by Vr.The results indicated that when Vr is larger,the inverse emulsion system is more stability.The stability of acrylamide and its derivatives inverse emulsions,prepared with surfactants consisting of lipophilic Span80/Span85 and hydrophilic tween80,was characterized by Vr.It is found that a positive correlation relationship exists between Vr and the mass fraction of oil phase.At a fixed mass fraction of oil phase,Vr is related not only to the hydrophilic-lipophilic balance(HLB) value of the three surfactants composite,but also to the concentration and type of acrylamide and its derivatives.When HLB value is about 4.20,the emulsion is stable;When the mass fraction of acryloyloxyethyl trimethyl ammonium chloride(DAC) in the aqueous phase is higher than 24%,the stable emulsion exist;When the mass fraction of DAC is lower than 24%,with the increase of DAC mass fraction in the aqueous phase,the inverse emulsion stability is improved too.It is observed that when Vr is greater than 0.95 by centrifuging for 3 min at 15000 r/min,the inverse emulsion of acrylamide and its derivatives is extremely stable,and the separation of emulsion phase did not occur in reserve even after half a year.