The voltage stability problem of load center threatens the safe operation of Hunan power grid due to the unbalanced distribution of loads and sources, especially after integrating with ±800 kV QiShao UHVDC transmission line in 2007. In this paper, the relationship between the transient voltage and angle stability is analyzed. In addition, the voltage stability is also analyzed for power grid integrated with UHVDC in the aspects of the effective short circuit ratio (ESCR), static voltage stability and load characteristics. It is shown that the sensitive spot, weak spot of voltage stability and the UHVDC links location are all located in Xiangdong power grid. The ESCR can be increased by shortening the electrical distance of the internal structure in Hunan power grid. However, the voltage sag would be more serious when suffering a large disturbance. The voltage stability level of Hunan grid can be improved effectively by reinforcing the connection between Hunan and Central China power grid. Since the grid structure cannot be strengthened within a short period, the transient voltage stability level of Hunan power grid can by improved by decreasing the short circuit capacity of Heling substation or optimizing the parameters of UHVDC inverter station.