The invention discloses a double-bus self-adaption sampling line selection device. The double-bus self-adaption sampling line selection device comprises a first bus, a second bus, a first voltage transformer, a second voltage transformer, a first switching circuit, a second switching circuit, a current transformer, a first analog signal acquisition circuit, a second analog signal acquisition circuit, a third analog signal acquisition circuit, a master controller and a main transformer. Through the switching circuit and control of the master controller, reactive power can be automatically collected and calculated. The double-bus self-adaption sampling line selection device can collect and calculate the reactive power of the main transformer correctly and reliably, guarantee the correctness and effectiveness of subsequent power quality control and provide accurate auxiliary calculation and measurement for effectively lowering loss of electric transmission lines.