In order to evaluate the influence of number of mixing elements on velocity distribution and turbulence，the flow field inside a Kenics static mixer(KSM) was measured by using laser Doppler velocimetry.The results showed that the velocity in the KSM was redistributed and the turbulence was strengthened due to the mixing elements.It took place primarily in the first three elements，in which the turbulence was strengthened but the rate of increase fell off along the mixing elements.And more important，the strengthening effect was most significant for the first element and the stabilized state was reached after the fourth element.When the number of the mixing elements was more than three，the limit of strengthening fluid turbulence was reached and the turbulence was no more strengthened by increasing the number of mixing elements.