In order to study the flow field characteristic of constraint abrasive fluid polishing, based on Navier-Stokes equation and continuity equation of fluid flow, the three dimensional mathematical model of fluid dynamic pressure in processing area of constrained wheel and workpieces was set up, and the fluid dynamic pressure was calculated by the simulation software of Matlab. The results show that the hydrodynamic pressure is inversely proportional to the minimum clearance and directly proportional to the constrained wheel speed during the constraint abrasive fluid polishing, the maximum pressure peak value occurs in the region of the minimum clearance between constrained wheel and workpieces, and the pressure gradient in the area changes significantly. A constrained abrasive jet polishing system was designed to polish the K9 glass samples. The results show that, to reduce the minimum clearance between constrained wheel and workpieces, and increase the constrained wheel speed, both can effectively improve the surface quality of workpieces. Combined with simulation and experimental results, it is shown that under certain conditions, with the increase of dynamic pressure in wedge zone, the abrasive in the contact area gains higher energy, and the surface quality of the glass is improved accordingly.