The work presents the results of numerical investigations of the effect of the load and velocity parameters of a mining truck moving over a long descending grade upon thermal conditions of the multidisc oil-cooled brake (MDOB) operation. The initial boundary-value problem for the heat transfer in the MDOB friction pair under frictional heating has been formulated and solved by the finite-element method. The computations performed for the friction pair of high-carbon steel against frictional composite material based on polymer binders. The effect of the load-velocity operation parameters on the thermal conditions of the mining truck MDOB was studied by way of a multifactor numerical experiment using a mathematical model of heat transfer in the MDOB friction pair. Regularities of the transient temperature field formation have been identified and approximate equation for dependence of the maximal temperature in the MDOB friction pair on the slope angle value of the downgrade, mass and speed of the mining truck was obtained. The regions of load-speed operation parameters of the mining truck have been estimated that corresponds to the allowable or critical thermal conditions of the MDOB design under study.