Abstract: Integrated energy systems（IES）, consisting of the coupling and interactions between electric power systems（EPS） and natural-gas systems（NGS）, are expected to play an important role in constructing the economic, eco-friendly, and efficient energy systems. Meanwhile, due to the fact that IES are confronted with a wide range of uncertainties, it is essential to take advantage of uncertainty modeling techniques to analyze IES. In this paper, the concept of probabilistic load flow, which has been widely applied in EPS, was extended to IES probabilistic energy flows analysis. Three aspects of coupling between EPS and NGS are considered: 1) gas-fired generators; 2) electric-driven compressors; and 3) energy hubs. Based on the models of IES steady energy flows, the proposal is solved by Monte Carlo simulation with the consideration of uncertainties of electric, gas and heat loads and wind farms output power. Finally, test results demonstrate that the uncertainties in NGS（or EPS） do have effects on EPS（or NGS） probabilistic energy flows. Further, the accuracy of linearizing NGS energy flow equations is obvious lower than EPS.