The present invention provides a permanent magnet synchronous motor decoupling vector control device in a two-phase stationary coordinate system and a method thereof. A rotation speed comparator carries out differential treatment on a rotation speed set value and a rotation speed feedback value, a current vector magnitude instruction is generated through a rotation speed controller, combined with a rotor position angle and a permanent magnet synchronous motor control strategy, alpha axis and beta axis instruction current is generated, two current controllers form closed loop control on the alpha axis and beta axis instruction current, alpha axis and beta axis voltage control amounts are generated, and a permanent magnet synchronous motor is controlled through a SVPWM module and a control voltage source inverter. A Clark transformation module converts the A and B phase current of the permanent magnet synchronous motor into alpha axis and beta axis current components. A position sensor detects the rotor position of the permanent magnet synchronous motor in real time, rotor position information is provided for an i<*>(alpha), i<*>(beta) synthesizer and the SVPWM module, and at the same time the rotation speed feedback value of the motor is obtained through a position differential module. According to the device and the method, the performance requirements for the controller are greatly reduced, and thus the cost of a frequency converter is reduced further.