Abstract: In low-Reynolds-number flow passing circular cylinder, fluid experiences a relatively complex process,for instance,the vortex in the near wake does not roll up and diffuse axisymmetrically.Field and Lagrange viewpoint were used to analyze flow field characteristic at fixed time and flow process during a time interval separately.Through the superposition of pressure contours and relative streamline, alleyway flow between votices was analyzed. The time-dependent fluid velocities were interpreted from the viewpoint of vortex structure.The standpoint that part of fluid was governed by distinct flow structures at different time gave insight to the phenomenon of substantial gaps between successive points in multiple folding steaklines.Several subzones were divided around the circular cylinder, the moving process and deformation of partial fluid were analyzed.