It is widely acknowledged that inhomogeneous and time-varying plasma can effectively reduce the back scattering radar cross section (RCS) and THz wave has the potential to penetrate the plasma and against the plasma stealth. Therefore, the backscattering and bistatic radar cross section (RCS) of conductor cylinder coated with parabolic distribution and time-varying plasma media in THz wave band are studied by the Runge-Kutta Exponential Time Differencing-Finite Difference Time Domain (RKETD-FDTD) method in this paper. The influences of plasma parameters are analyzed. From both the backscattering and bistatic RCS simulations, it is obviously that inhomogeneous and time-varying plasma cloaking system makes a significant difference on reducing the RCS and improve the plasma stealth while electromagnetic wave in THz region can successfully weaken its influence and contribute to the anti-stealth.