The invention discloses an alternating current voltage acquisition device and a working method thereof. The alternating current voltage acquisition device is characterized in the that the acquisition device comprises a current limiting branch circuit, an alternating current voltage conversion branch circuit, a direct current bias voltage branch circuit, an impedance transformation and following branch circuit and a software processing branch circuit which are connected with one another successively, wherein the current limiting branch circuit is connected with a measured alternating current voltage input end. With the alternating current voltage acquisition device and the working method thereof of the invention adopted, the influence of a main temperature drift device can be reduced in a certain temperature range, and measurement accuracy can be improved, and measurement errors can be reduced; and a processing method is simple, and cost is low. The alternating current voltage acquisition device and the working method thereof are suitable for large-scale popularization and use.