Abstract: Parallel hanger cables and stay cables are used extensively in cable-supported bridges. However, the cross-wind mean lift of downstream cables induced by wake interference received little attention when calculating the wind loads on parallel cables. At Reynolds numbers between 0.9×10⁵~4.6×10⁵ (subcritical Reynolds regime and critical Reynolds regime), the aerodynamic characteristics of twin circular cylinders were investigated along with their relationships with the Reynolds numbers through a series of wind tunnel tests. Results show the mean aerodynamic forces of two circular cylinders in the critical regime were very different from those in the subcritical regime, showing strong Reynolds number effects. Furthermore, at the critical regime, the mean lift coefficients of the downstream circular cylinder discontinuously suffered abrupt change with the increase in the Reynolds number for some arrangements of the cylinders, which might be related to the shift of the flow state between different flow patterns. Under the wake interference of the upstream circular cylinder, the magnitude of the mean lift coefficient on the downstream cylinder was up to 1.25. Therefore, it is necessary to include the effect of mean lift when calculating static wind loads on parallel cables.