The burrs in the inner channel and intersecting part of the complex structure made by alloy materials are difficult to be removed effectively, and the AFM processing technology can effectively polish the complex surface of the parts and improve the machining quality of the workpiece. Based on this,the surface roughness and expanded diameter of the workpiece under the action of the unidirectional abrasive flow with different working pressures were studied,an on-line measuring device for the axial force of the unidirectional AFM was introduced,the influence of the different processing pressure and the length of the fluid channel on the axial force and the volume flow was analyzed.The results show that the AFM machining under 4 MPa pressure can effectively reduce the surface roughness of the workpiece and make the workpiece get more uniform surface roughness.However, the processing time of 4 MPa is longer than that of 7 MPa.The shorter the length of the fluid channel, the greater the volume flow with the increase of the piston pressure than the axial force. And for the longest fluid channel,the increase of the piston pressure leads to the increase of the axial force.