The results of existed study show that there is no requirement for reactive compensation by Half Wavelength Al-ternating Current Transmission (HWACT) lines themselves. However, the characteristics of steady-state voltage distribution of HWACT lines are distinctive. The over-voltage maximum and its position are closely related with both transmission power and power factor. In this paper, based on parameters of existed ultra-high voltage AC transmission lines, steady-state voltage distribution characteristics of an HWACT line are firstly analyzed through digital simulation. Then with the aid of the voltage and current phasor diagram, both series compensation and shunt compensation at the terminals of the HWACT line instead of itself are proposed to improve the voltage distribution characteristics and to reduce power losses. The simulation and analysis results finally show that there are re-quirement for reactive compensation at the terminals of HWACT lines. Both series compensation and shunt com-pensation might reduce the power losses of the HWACT lines and modify the steady-state voltage distribution. The shunt compensation is more effective and easier to mitigate the steady state over-voltage of the HWACT line than the series compensation.