The invention discloses a rock-soil parameter random field inversion method. The method comprises the following steps: analyzing conventional statistical characteristics, spatial correlation structures and spatial correlation functions of rock-soil parameters; according to the precision requirement of geotechnical engineering reliability analysis, determining the calculation range of the spatial correlation of the geotechnical parameters; constructing a spatial correlation matrix B according to the calculation range of the spatial correlation and the grid size of the engineering analysis numerical model; solving a coefficient vector c according to the spatial correlation matrix B; utilizing a pseudo-random program to assign an initial random value to each grid of the engineering analysis numerical model, and generating an initial random field; depending on basic inversion equations, performing cyclic operation on each grid in sequence; generating parametric random fields, wherein the basic inversion equation is shown in the specification; wherein x (p, q) = m (p, q) + sigma(p, q) cTu, in the formula, x (p, q) is a parameter random value of any grid (p, q), m (p, q) is a mean valueat the grid (p, q), sigma(p, q) is a standard deviation at the grid (p, q), c is a coefficient vector, and u is an initial random vector which is generated based on an initial random field and influences parameter value at (p,q).