A quantitative calculation computer-implemented method for oil or gas saturation of a fractured reservoir, characterised by comprising the steps of: S1) obtaining a relationship between resistivity index and water saturation (Sw) of a fractured reservoir matrix on the basis of known full diameter core experiment data; obtaining real water, oil or gas saturation of original formation of the fractured reservoir on the basis of sealed coring analysis data; S2) obtaining fracture porosities at different depth of the fractured reservoir using known imaging logging data; calculating resistivity indexes at different depth using dual laterolog data combined with core analysis data; S3) establishing a percolation network model including matrix and fracture according to known pore structure features, porosity and permeability of a region of the fractured reservoir, and determining the relationship between the resistivity index and water saturation (Sw) in the fractured reservoir by drainage modelling; S4) calibrating numerical simulation results of the percolation network model using the full diameter core experiment data and the sealed coring analysis data; S5) after calibration, obtaining variation relationships between the resistivity index and the water saturation (Sw) under different fracture porosities by numerical simulations; S6) obtaining functions between the resistivity index and the water saturation at different fracture porosities by interpolation based on the obtained variation relationships; and S7) calculating the oil or gas saturation of the fractured reservoir according to the fracture porosity obtained from step S2), by choosing a function from the functions obtained in step S6), wherein the functions obtained in step S6) are as follows: I = a e b S w − c where, I is the resistivity index, S w is the water saturation, and a, b, and c are constants, when the matrix porosity is 3% and the fracture porosity is 0.0%: a=0.03, b=3.44, c=0.52; when the matrix porosity is 3% and the fracture porosity is 0.1%: a=0.06, b=2.70, c=0.52; when the matrix porosity is 3% and the fracture porosity is 0.2%: a=0.20, b=1.47, c=0.67; when the matrix porosity is 3% and the fracture porosity is 0.3%: a=0.38, b=0.85, c=0.77; when the matrix porosity is 3% and the fracture porosity is 0.4%: a=0.52, b=0.53, c=0.91. S1) obtaining a relationship between resistivity index and water saturation (Sw) of a fractured reservoir matrix on the basis of known full diameter core experiment data; obtaining real water, oil or gas saturation of original formation of the fractured reservoir on the basis of sealed coring analysis data; S2) obtaining fracture porosities at different depth of the fractured reservoir using known imaging logging data; calculating resistivity indexes at different depth using dual laterolog data combined with core analysis data; S3) establishing a percolation network model including matrix and fracture according to known pore structure features, porosity and permeability of a region of the fractured reservoir, and determining the relationship between the resistivity index and water saturation (Sw) in the fractured reservoir by drainage modelling; S4) calibrating numerical simulation results of the percolation network model using the full diameter core experiment data and the sealed coring analysis data; S5) after calibration, obtaining variation relationships between the resistivity index and the water saturation (Sw) under different fracture porosities by numerical simulations; S6) obtaining functions between the resistivity index and the water saturation at different fracture porosities by interpolation based on the obtained variation relationships; and S7) calculating the oil or gas saturation of the fractured reservoir according to the fracture porosity obtained from step S2), by choosing a function from the functions obtained in step S6), wherein the functions obtained in step S6) are as follows: I = a e b S w − c where, I is the resistivity index, S w is the water saturation, and a, b, and c are constants, when the matrix porosity is 3% and the fracture porosity is 0.0%: a=0.03, b=3.44, c=0.52; when the matrix porosity is 3% and the fracture porosity is 0.1%: a=0.06, b=2.70, c=0.52; when the matrix porosity is 3% and the fracture porosity is 0.2%: a=0.20, b=1.47, c=0.67; when the matrix porosity is 3% and the fracture porosity is 0.3%: a=0.38, b=0.85, c=0.77; when the matrix porosity is 3% and the fracture porosity is 0.4%: a=0.52, b=0.53, c=0.91. where, I is the resistivity index, S w is the water saturation, and a, b, and c are constants, when the matrix porosity is 3% and the fracture porosity is 0.0%: a=0.03, b=3.44, c=0.52; when the matrix porosity is 3% and the fracture porosity is 0.1%: a=0.06, b=2.70, c=0.52; when the matrix porosity is 3% and the fracture porosity is 0.2%: a=0.20, b=1.47, c=0.67; when the matrix porosity is 3% and the fracture porosity is 0.3%: a=0.38, b=0.85, c=0.77; when the matrix porosity is 3% and the fracture porosity is 0.4%: a=0.52, b=0.53, c=0.91.