The invention discloses a high precision impedance measuring device based on UPQC and a switching control method thereof. The abovementioned device comprises a UPQC disturbance injection unit, a signal processing unit, a broadband impedance calculating and monitoring unit, and a control unit. The serial connection side of the UPQC disturbance injection unit is serially connected with a to be measured system by a coupling transformer, and the parallel connection side thereof is directly parallely connected with the to be measured system. When impedance of a power grid is higher than impedance of to be measured equipment, current disturbances are injected in the parallel connection side, and the serial connection side is used to stabilize direct current side voltage; when the impedance of the power grid is lower than the impedance of the to be measured equipment, the current disturbances are injected in the serial connection side, and the parallel connection side is used to stabilize thedirect current side voltage, and then the disturbances are distributed on the side of the to be measured equipment at high proportion to improve impedance measuring precision.