With the development of quantum radar technology, the interaction of photons and targets has gradually become a new hotspot. Quantum radar cross section (QRCS) is an important parameter fon describing the visibility of the target illuminated by light quantum. #br#According to the conservation of energy and the finite element method, the expression of QRCS derived by Marco Lanzagorta is extended, which can be applied to QRCS calculations of non-planar convex targets. As the surface elements of the target have different incident and scattering angles, the integral equation can give a higher calculation accuracy and is suitable for bistatic or multistatic situations. #br#The distribution pattern of the target’s atoms is varied. Using the interatomic distance as the only parameter to describe the atomic distribution is inaccurate. In this paper the metal atomic lattice is considered. Simulation of the QRCS that is composed of three kinds of metal atomic lattices (face-centered cubic, body-centered cubic and hexagonal close-packed lattices) with different atomic distributions has been made. The hexagonal close-packed lattice with asymmetrical distribution for different azimuth angles is discussed. Simulation result shows that with different arrangement of atoms, the main lobe of the target QRCS is basically unchanged, while the quantum side-lobes of the target with sparsely arranged atoms are much more significant. This reveals a different characteristic of QRCS, and provides theoretic basis for quantum radar and stealth technique researches.