Free abrasive wiresaw technology is the main method in slicing monocrystalline silicon wafers. The mathematical model of hydrodynamic action in the process of the free abrasive wiresaw slicing was founded, displacement caused under distributed radial load of every node on the wire is embodimented through self-compliance influence coefficient, which is beneficial to found the film thickness equation. The distributions of hydrodynamic pressure and film thickness in the free abrasive wiresaw slicing process are yielded by using the finite difference numerical methods to solve the two-dimension Reynolds equation. The results show that the minimum film thickness increases with the increase of wire speed, and slurry viscosity, while decreases with the increase of wire bow angle. The film thickness is greater than the average abrasive size so that the abrasives float in the slurry when the size of abrasive is small enough.