The invention relates to a new method of advance geology forecast. For a three-dimensional resistivity inversion problem, the amount of observation data is usually smaller than the number of unknown parameters, and due to errors of the observation data and other reasons, a strong correlation usually exists between equations; under the circumstance, the inversion problem is manifested as a mixed determined problem; to solve the problems, prior information needs to be applied into model construction. According to the new method of advance geology forecast, smooth constraint serves as the prior information to be applied into the inversion equation, wherein the smooth constraint means smooth transition of resistivity values of adjacent grids, that is to say, the difference between the resistivities of the adjacent grids is made extremely small, and thus a simplest three-dimensional geophysical model is constructed; the smooth constraint has natural reasonability, because the essential features of the model are maintained; due to application of the smooth constraint, the ill-posedness of the inversion equation is greatly reduced.