This paper summarizes the development of the probabilistic load modeling for the turbomachinery of space propulsion systems at Rocketdyne. The demand for rocket engine turbomachinery with high performance and light weight has presented a unique set of problems; e.g., the high-energy density in design and analysis of the turbomachinery loads. A heuristic approach to the simulation of probabilistic loads is employed to provide a uniform framework on which the subsystem component loads are evaluated.Turbomachinery loads can be classified into three categories: (1) loads internal to the turbopumps, (2) loads that result from the turbopump operation, and (3) loads transmitted from other driving sources. The modeling techniques employed for the turbomachinery loads are the influence model method, the marginal distribution method, the scaling method, the normalized power spectral density (PSD) model, and improved scaling for vibration, etc. Examples of the probabilistic load models for each category are presented to illustrate the modeling methodology.