Abstract: Five-axis gantry machining centers constitute the core foundational equipment of modern manufacturing, and their technological sophistication directly determines the capability for producing high-precision components in aerospace, aviation, automotive, shipbuilding, energy, and other industries. Geometric error is one of the primary error sources in five-axis gantry machining centers. However, the 41 error items of five-axis machine tools are subject to intricate nonlinear coupling, posing significant challenges to their efficient measurement, identification, and compensation. A multilateral measurement method was proposed for identifying the geometric errors of both linear and rotary axes, along with a real-time compensation strategy for five-axis errors. Dedicated software for geometric error identification and compensation of five-axis machine tools was developed. Using an AC swing head five-axis machining center as the experimental platform, efficient measurement, identification, and real-time compensation experiments for geometric errors were conducted. The results confirm the correctness and effectiveness of the proposed identification and compensation methods.