The construction of Shandong — Hebei UHV loop network will lead to great changes in the grid structure of North China Power Grid and the operation risk is outstanding, it is urgent to study the system safety and stability control measures. The safety and stability control analysis process of UHV AC/DC system is proposed based on the characteristics of grid structure. Two types of major power grid stability problems and corresponding control measures under N-2 faults of UHV AC system are mainly studied, including the wide-area coupling problem of UHV AC-DC system and the voltage collapse problem of multi-infeed DC coupled with receiving power grid. On this basis, the optimization measures to reduce load shedding are put forward. The results show that the proposed safety control measures can effectively support the stable operation of the power grid after the construction of the UHV loop network. This work is supported by National Natural Science Foundation of China (No. 51777196) and Science and Technology Project of State Grid Corporation of China (No. XT-71-18-036).