Abstract: Inner vortex speeding cyclone collector is very different from traditional cyclone dust collector in the structure． The flowfield distribution and the dust separating procedure are different too. The separation areas are divided into different areas， such as outer vortex area,inner vortex area, mixing vortex area and central vortex area. The inner vortex area is divided into two parts: upper part and lower part. The bound form of the flow structure and the dust separation are similar to the outer vortex area. This paper investigated the flowfield distribution of the inner vortex speeding cyclone dust collector both in outer vortex area and in inner vortex area．The airflow velocity was measured and the three dimension vector of the flowfield distribution was derived. The test results showed that:1)tangent velocity distribution of flowfield is quasifree vortex,index of the quasifree vortex is 0.5, the minimum tangential velocity is 15 m/s in the outer vortex area and 35 m/s in the inner vortex area;2)the axes velocity distribution is index form in the outer vortex area and in the upper part of the inner vortex area,the maximum axes velocities are 4.92 m／s and 5.57 m／s respectively, and the axial velocity in lower part of the inner vortex area increases along the radial direction;3)radial velocities in both outer and inner vortex arial are centripetal and very small.