The two-stage synchronous starter-generator (TSSG) system is a good candidate for the more-electric aircraft (MEA) integrated starter-generator (ISG) system due to the high reliability and good power generation quality. The accurate model of TSSG is necessary for the detailed analysis and advanced control research. However, separated modeling of brushless exciter (BE) or main machine (MM) cannot reflect the coupling relationship, so it is necessary to establish the integrated model of the TSSG including BE, rotating rectifier and MM. In this paper, two integrated models of TSSG based on double-side Voltage-Behind-Reactance (VBR) and state-space equations, respectively, are proposed considering magnetic saturation, and comparative simulation was carried out to verify these models.