This work aims to analyze the effects of mechanism and process parameters of medium flow filed on the processing capacity during the spindle-type barrel finishing. Based on mixture model, standard k-ε turbulence model and pressure-velocity coupled SIMPLEC algorithm, numerical simulation was performed for the solid-liquid two-phase turbulent flow composed by the medium flow field in spindle barrel finishing process. The distribution of abrasive velocity vector and workpiece surface pressure under different parameters was analyzed by changing the process parameters like barrel speed, distance from workpiece axis to the barrel wall. The effectiveness of the simulation was verified by test experiments. The maximum point of static pressure was 32 MPa at 0°, the maximum point of dynamic pressure was about 35 MPa at 90° and 270°, and the total pressure in the wake area was greatly reduced to 33% at 0°. The total pressure on the workpiece surface was exponentially related to the rotation speed of the drum. When the rotating speed was more than 50 r/min, the total pressure value reached 32 MPa at 0° and 270° and increased rapidly. In the area where the distance between the axis of the workpiece and the wall of the drum was 65 mm, the maximum total pressure of the workpiece surface was 19 MPa. When the distance was 30 mm, the total pressure was negative at 270° due to the effect on abrasive by drum wall. The average pressure error between numerical simulation and experimental results was 5.25%. The part on the workpiece facing abrasive is subject to impact and compression, while two sides are subject to scratching effect. When the rotating speed is greater than 50 r/min and the distance between the axis of the workpiece and the wall is 65 mm, the machining ability of the abrasive is relatively strong.