This study numerically investigates the spreading and retracting dynamics of Janus drops on the inner surfaces of cylinders using the Volume of Fluid method. The results indicate that increasing surface curvature enhances spreading in the axial direction and promotes the detachment of the low-viscosity water component, particularly under conditions of high viscosity ratio and Weber number. A regime map is constructed to identify the critical conditions for separation, revealing that surfaces with intermediate curvature exhibit higher separation efficiency compared to those with high curvature. The temporal evolution of axial momenta in the x and z directions highlights the role of viscosity contrast in inducing asymmetric deformation. A scaling law for residence time is proposed as a function of Weber number, which aligns well with simulation results in the high Weber number regime. These findings provide fundamental insights for optimizing surface curvature and fluid composition to enhance drop separation and may benefit applications such as selective liquid extraction, surface cleaning, and microfluidic manipulation.