This document specifies the terms and definitions, symbols and descriptions, test principles, test equipment, specimens, test procedures, expression of test results and test reports of the cross-shaped in-plane biaxial fatigue test method for metal materials. This document is applicable to biaxial fatigue testing of metal materials using cross-shaped specimens at room temperature or high temperature to apply constant amplitude loading waveforms on each loading axis to achieve proportional or non-proportional loading paths and path transformations.