Abstract: In order to research on the axial velocity's distributing law of power law fluid's helical flow in eccentric annulus an experimental model and scheme of fluid's helical flow in eccentric vertical annulus was established.Particle images in various flow fields of helical flow in eccentric annulus were shot by PIV (Particle Image Velocimetry) system.The dada were analyzed and the main affecting factors of the axial velocity's distributing law of power law fluid's helical flow in eccentric annulus were defined.The law of pressure gradient,viscosity,inner pipe's revolution and eccentricity's influence on axial velocity distribution of eccentric annulus's wide and narrow interspace were analysed with great emphasis in this paper.