Genetic Algorithm Combining Operation Tree (GAOT) was constructed to estimate the slump flow of high-performance concrete (HPC) by using seven concrete ingredients. HPC is a highly complex material; because modeling its behavior is extremely difficult, robust optimization techniques are required. GAOT is a type of evolutionary algorithm that simultaneously optimizes functions and their associated coefficients and is suitable for automatically discovering relationships between nonlinear systems. In a case study, it was observed that for estimating HPC slump flow, the GAOT is more accurate than regression model and back-propagation neural networks (BPNN).