The invention relates to a determination method of organic porosity of a shale gas reservoir based on well logging data. The method comprises following steps: collecting shale gas reservoir organic porosity data and shale gas reservoir well logging data obtained through work area parameter well core experimental analysis; calculating inspected organic matter maturity Roa1 of the parameter well shale gas reservoir; calculating organic porosity [phi]toca1 of the parameter well inspected shale gas reservoir; obtaining organic porosity coefficient K of the work area shale gas reservoir by means of the cross-plot technology; collecting well logging data of the shale gas reservoir to be processed; calculating the reservoir inspected organic matter maturity Roa; calculating the organic porosity [phi]toca of the inspected shale gas reservoir of the well to be processed; calculating the organic porosity [phi] toc of the gas reservoir; outputting the calculation results of the organic porosity [phi]toc of the shale gas reservoir of the well to be processed. By means of the method, reliable data is provided for shale gas reservoir evaluation and prediction rate is increased. The method is simple and has wide application scope. The method is applied in 182 wells in Fuling shale gas field, and the prediction rate is high.