Abstract: The steady cross-flow past a circular cylinder in the lowReynolds numbers was investigated using non-equilibrium molecular dynamicssimulations with the Lennard--Jones potential. The results showed threebasic flow patterns in microscale, different from those in macroscale. Theflow behind the circular cylinder is symmetric, nonseparated and steady whenRe<12. Periodic shedding and the oscillation of vortices are observed whenRe>20. When the stream velocity is higher than the local sound speed, acavity in the downstream adjacent to the cylinder forms. Asymmetric vorticesappears as a transitional range when 12