The determination of proppant settling velocity in fracturing fluids is of significant importance in fracturing design. In order to characterize proppant shape and surface roughness effect on its settling velocity, equivalent hydraulic diameter of proppant settling in 0.1% wt polyacrylamide solution was presented. According to the measured proppant geometric diameter using image analysis, the correlation between equivalent hydraulic diameter and geometric diameter has been established, and goodness of fit is perfect with average relative error of 4.21%. Comparison between proppant equivalent hydraulic diameter and its Stokes diameter falling in glycerol has been conducted, and the proppant Stokes diameter is larger than the geometric diameter. However, due to the shear-thinning property and low apparent viscosity of 0.1% wt polyacrylamide solution, the proppant equivalent hydraulic diameter is smaller than the geometric diameter.