To further study the steady-state characteristics of brushless doubly-fed machine(BDFM) with squirrel-rotor，the basic equations are given according to the coupling circuits of BDFM. And then，the mathematical models of BDFM current，active power，reactive power，electromagnetic torque and power factor are analyzed and derived respectively. Furthermore，the characteristics of torque-angle，torque-frequency，power-angle，reactive power，power factor and V-shaped curve of BDFM are obtained respectively by MATLAB simulation of a prototype. The energy conversion of BDFM is analyzed by the proposed mathematical models at the same time. The results show that all the steady-state characteristics of BDFM can be expressed as the functions of the control windings voltage，frequency and the power angle. The proposed model simplifies the analysis of the steady-state characteristics of BDFM and provides a theoretical foundation for the further study on operating stability and control strategy of BDFM.