Abstract: Flexible AC transmission system（FACTS） devices such as static synchronous compensator（STATCOM） and static synchronous serious compensator（SSSC） have been used in real power grids.The voltage stability assessment of a hybrid power system with FACTS is important.Based on the source-impedance models of STATCOM and SSSC,the load flow model of a power system with STATCOM and SSSC is developed.The alterative-iteration method embedded into Newton power flow method is used to solve this problem.A double switching logic is proposed for handling the operation constraints of STATCOM and SSSC.A continuation power flow method considering FACTS is presented for calculating the load margins and voltage stability critical points.An identification scheme of saddle node bifurcation point（SNBP） and limit induced bifurcation point（LIBP） induced by the operation limits of STATCOM and SSSC is also given.The numerical results on IEEE 30-bus and IEEE 118-bus test systems show that the method proposed is efficient and suitable for voltage stability assessment of power systems with FACTS devices.