The invention relates to a logging well method for rapidly predicting the formation rupture pressure gradient of a shale gas layer, which comprises the following steps of: obtaining the lithology density Rhob data of the shale gas layer, wherein the measuring unit is g/cm<3>; acquiring the fluid pressure gradient (FPG) data of the pore of the logging while drilling in the shale gas layer of the well, and predicting the formation rupture pressure gradient FRAC of the shale gas layer of the well, wherein the prediction model is FRAC=(pb+FPG)/2; outputting the prediction result. The method is applied to more than 300 wells at Fuling shale gas field in southern Sichuan of Sichuan Basin, compared with the results obtained by other methods, the method has the advantages that the average error isless than 15%, the speed is fast, the cost is low, and the working requirement of rapidly predicting the formation rupture pressure gradient of the shale gas layer in the field logging well can be met, the method provides an important work basis for fracturing and reformation, optimizing drilling and safe drilling of the shale gas layer.