The speed-adjustable system of asynchronous motor has been widely used in industrial production. in motor control, magnetic control is a key problem, but in order to realize the control of motor, magnetic field must be tested. The testing methods about rotor flux according to the rotor field-oriented control of motor are discussed in this paper. The paper describes the present two rotor flux calculation models: Voltage model and Current model. It concretely analyzes mathematical expressions of these two models in different coordinates, and realizes the matlab simulation of two kinds of model, the simulation results are compared by observations of the magnetic chain calculation results.