The invention provides a method for obtaining crustal stress based on three-dimensional prestack seismic inversion results. The method comprises the steps of: firstly, reading a bursting pressure, aninstantaneous stop pumping pressure and a crack re-tension pressure by using a hydraulic fracturing method, and calculating maximum horizontal principal stress and minimum horizontal principal stress;carry outing prestack seismic inversion to obtain inversion results, such as longitudinal wave impedance, velocity ratio of longitudinal and transverse waves, density, and calculating elastic parameters such as Young modulus and Poisson ratio; performing reverse demarcation on the elastic parameters according to a logging interpretation crustal stress formula by using the read maximum horizontalprincipal stress and the minimum horizontal principal stress to obtain tectonic stress coefficients; and finally calculating the elastic parameters by using the tectonic stress coefficients to obtaina three-dimensional crustal stress result. The method is expanded on the conventional logging data crustal stress calculation method, and the calculation method of a single well is expanded to three-dimensional seismic inversion; the hydraulic fracturing data are fully combined, so that the final three-dimensional crustal stress result has higher accuracy and reliability, and the elastic parameters of "dynamic" and "static" states do not need to be converted again.