The embodiments of the invention disclose a comprehensive evaluation method and device for oil and gas reservoir rock. The method comprises the following steps that: a target reservoir rock core is acquired, and a test rock core is intercepted; the porosity, permeability and fluid saturation of the test rock core are obtained through a nuclear magnetic resonance experiment, and are subjected to normalization processing; a reservoir rock oil-gas possibility evaluation model is established, and a reservoir rock oil-gas possibility index is calculated; the test core is fractured through triaxialmechanical experiment equipment, and the fracture fractal dimension value of the fractured rock sample is calculated through a box-counting dimension method; a rupture angle is calculated; the reservoir three-dimensional fracturing performance evaluation model of tight sandstone is determined according to the reservoir rock oil-gas possibility index, the fracture fractal dimension value and the rupture angle; and the fracturing performance of reservoir rock in a target area is evaluated through the reservoir three-dimensional fracturing performance evaluation model. With the method and deviceprovided by the technical schemes provided by the invention adopted, the comprehensive evaluation method for the oil and gas reservoir rock can be realized, and the evaluation accuracy of the oil andgas reservoir rock is improved.