The integrated energy system contains a large number of uncertain factors,so it is necessary to consider the operating state of the integrated energy system in an uncertain environment. Based on the analytical method and the approximate method,a rapid calculation method for the probability power flow of a radial heating network is proposed in this paper. Firstly,the mean and variance of the mass flow rate within a pipe are obtained through the digital characteristics of the normal distribution function. Then,the mean and variance of the node temperature are calculated by the properties of continuous random variables. When the probability distribution of the heat output of the combined heating and power (CHP) unit is calculated,the probability distribution of the electric output of the unit is obtained. Finally the probability distribution of each state variable of the power system is calculated. The method proposed in this paper is able to calculate steady state power flow and probability power flow without iteration,and there is no convergence problem. The method greatly improves the calculation speed while ensuring the calculation accuracy,which provides a reference for the uncertainty analysis and risk assessment of the integrated energy system.