<p>In a heavy-loaded horizontal-rotor system, continuous crack closure leads to an open crack state where no more switching occurs. In this paper, we formulate the finite element stiffness matrix using the area moment of inertia and coordinate transformation of the crack section about the neutral axis before the shaft rotates, and derive the equations of motion of a hollow shaft rotor system with a transverse open crack. To solve the finite element model of the rotor bearing disc system, the harmonic balance method (HBM) is used. As a next step of crack opening, the simulation results of an open cracked hollow axis system show some unique results that can be used to detect cracks in the hollow axis. In the open-crack system, the fractional harmonics of the first positive vortex frequency are not excited, and in the case of deep cracks, a sudden decrease of the positive vortex frequencies occurs. As the crack element moves away from the bearing, the first positive vortex velocity increases and the reverse vortex velocity decrease. And the variation of the axial locus of the rotor system with the couple unbalance was very slow. The finite element model of the hollow shaft system is also presented and we use the harmonic balance method(HBM) to analyze at the critical and subcritical speeds of the hollow shaft system. This study was compared with the behavior of a general shaft with open cracks. The results showed that the simulation results of open cracked hollow shaft system showed similar behavior to those reported in the literature for general shaft and were efficient in detecting cracks in hollow shaft.</p>