Lugaozhao DC project is the first high voltage, large capacity, multi-terminal LCC based DC system in China. It is reconstructed based on a two-terminal DC system, and has various operation modes to realize the mutual support of Yunnan hydropower resources and Guizhou thermal power resources and to relieve the provincial power balance pressure. According to the multi-terminal operation characteristics and fault behavior of Lugaozhao DC project, this work mainly analyzes the system stability and control measures of the DC polar faults, DC line faults, bipolar zone faults under three-terminal operation mode. Furthermore, to handle the key problem of multi-terminal DC power loss calculation method, converter station polarity reversal phenomenon, and adaptability of control strategy, security and stability control strategy and system architecture are proposed for multi-terminal DC systems. The presented security and stability control system provides a strong support for the mature application and promotion of multi-terminal DC technology in China.