The invention discloses a static pressure oil film compensation method for increasing the coaxiality of boring processing comprising following steps: S1. predicting and calculating the deflection deformation difference of boring cutter points according to the position shift of axial movement of a boring machine main shaft; S2. calculating the oil film thickness compensation of the front and rear static pressure guide rail support of the headstock according to the deflection deformation difference; S3. determining the target pressure and target flow of oil chambers of the front and rear static pressure guide rail supports according to the oil film thickness compensation and the inherent properties of static pressure guide rail supports; S4. adjusting the real-time pressure and real-time flow of each oil chamber according to the target pressure and target flow of each oil chamber and changing the thickness of oil films so as to make the headstock generate expected compensation inclination amount to realize the object that the boring cutter point positions are kept unchanged before and after the movement of the main shaft. By means of the static pressure oil film compensation method for increasing the coaxiality of boring processing, the compensation structure of boring machine headstock is simplified, the raw material and energy consumption are reduced and machine structure is compacted; the method is easy to control and has high reliability.