The invention discloses a method for calculating oil saturation of a reservoir. The method comprises the following steps of: establishing a reservoir oil saturation model including a
free fluid porosity phi f, a bound fluid
porosity phi b, as well as corresponding
macropore bond index mf, micropore bond index mb and micropore bond index characteristic value parameters; measuring a core
porosity phi of a selected
core sample; carrying out a
nuclear magnetic resonance T2 spectrum experiment and an electric petrophysical experiment on the selected
core sample to determine the core porosity phi and
bound water saturation Swir of the selected
core sample, the
free fluid porosity phi f and bound fluid porosity phi b, stratum water resistivity Rw of a saturated
rock sample, saturated water rock resistivity Ro of each
rock sample, and resistivity Rt of each rock under different conditions of
water saturation Sw; determining parameters of a reservoir oil saturation model by adopting an optimization data fitting method; establishing a relationship between the core micropore bond index mb and the
bound water saturation Swir; classifying reservoir cores according to the
bound water saturation; and determining a
saturation index n of each type of cores by using the optimization
fitting algorithm.