The article discusses the current problem of ensuring the reliability of technical systems, which is one of the important indicators of quality and competitiveness. The purpose of this article is to consider the problem of predicting the reliability of robotic machines with a parallel structure (parallel kinematics) at the initial stages of design. An important parametric characteristic of robotic machines is the positioning accuracy of the working element, its stability, and the preservation of values within specified limits over time. A methodology for predicting the parametric reliability of a robotic machine, which is designed according to a hexapod (Stewart platform) with electro-hydraulic control, is considered. The method of independent expert assessment or the method of rank correlation, which is based on statistical and heuristic processing of expert opinions, was used. Experts assigned each factor a corresponding rank, depending on the degree of its influence on the parametric reliability of the robotic machine. The arithmetic mean weight, the average relative weight, the standard deviation of the factors, and the coefficient of variation were calculated. Conclusions about the consistency of expert opinions are formulated based on the general set of characteristics and factors using the concordance coefficient (Kendall criterion). The considered methodology can be used to predict and assess the reliability of all types of robotic machines.