AbstractFor better revealing the behavior and mechanism of fatigue short crack (SC) propagation, five different kinds of notched samples were designed. Based on the crack growth rate‐SC length map, finite element method and electron backscatter diffraction (EBSD) pattern, the evolution theory of geometrically necessary dislocation density (ρGND) versus SC length was proposed to distinguish the physically short crack (PSC) length; Schmid factor was utilized to define the length of microstructurally short crack (MSC). Thus, the whole SC growth was divided into three parts: MSC, transition zone and PSC. Finally, an original piecewise model containing two parameters was proposed to describe the whole SC growth of EH36 steels.