Traditional finishing technology is difficult to realize the precision machining of complex geometric parts. Abrasive flow machining technology solves this problem well. Taking the spur internal gear as the research object, the wall shear force, static pressure, dynamic pressure and abrasive velocity vector of the internal channel of the straight internal gear under different inlet velocity, abrasive concentration and abrasive particle size are analyzed by using the large eddy simulation method, and the action law of different parameters on the machining of straight internal gear by solid-liquid two-phase abrasive flow is discussed. At the same time, orthogonal test was carried out. The results show that the solid-liquid two-phase abrasive flow machining technology can effectively remove the burrs, pits and bulges on the tooth surface of spur internal gear, reduce the tooth surface roughness and improve the surface quality. The optimal combination of processing parameters and the primary and secondary order of various factors affecting processing are obtained by range analysis and analysis of variance. The regression equation is constructed by regression analysis to verify the effectiveness and accuracy of the model, which provides theoretical support and data reference for actual processing and production.