Due to the small scale of the network and its weak grid structure, Qinghai-Tibet HVDC interconnection project will pose great challenges to the safe and stable operation of the Central Tibet power grid, especially to AC/DC system stability. Based on the inherent characteristics such as large-unit and small-grid, and features of the power sources and so on, and considering all the security and stability problems under operation of Central Tibet power grid and Qinghai-Tibet HVDC after the interconnection project put into operation, this paper makes a deep analysis of various changes in operating characteristics like the sources features, stability property, Huqu-line power transmission capability, DC commutation failure, and AC and DC interactions. Additionally, several significant and special operating requirements of Qinghai-Tibet HVDC are also analyzed and proposed on the premise of the safety and stability of Central Tibet power grid.