The epsilon ε,which is introduced in Omega vortex identification criterion(Ω method)proposed by Liu et al.[1],has been determined as a function ε = 0.001(b-a)max for removing noise case by case.Several typical dimensional cases are chosen to test the function of ε and improve the Ω method to be with ε auto-adjustment.After the determination of ε,the advantages of the Ω method can be rewritten as follows:(1)The Omega criterion is a normalized,functional and nocase-related method which has a threshold of 0~1 and represents the degree of the vorticity overtakes deformation;(2)Compared with Q and λ2 iso-surface visualization,which requires wide thresholds to properly capture the vortex,Ω = 0.52 can always capture both strong and weak vortices in all the cases at different time steps,without noise in the space;(3)Since the Ω method can capture both strong and weak vortices simultaneously,it cannot show the strength of vortex; however,the vorticity can be used to color the vortex structure for the visualization of the vorticity strength;(4).The epsilon ε is defined as a function of a fixed parameter for each case,which is the maximum of b-a,that means the epsilon doesnt need adjustment any more.