The invention discloses a low-voltage power line carrier channel attenuation characteristic test system and a control method thereof. The low-voltage power line carrier channel attenuation characteristic test system comprises a test unit I and a test unit II, wherein both the test unit I and the test unit II are formed by carrier signal transceiving devices and data processing devices. The carrier signal transceiving devices receive data of a power grid and then transmit the data to the data processing devices to perform an attenuation test. The control method of the low-voltage power line carrier channel attenuation characteristic test system comprises the steps that a forward attenuation test is performed: after one of the test units transmits a carrier signal to a power line network, the two test units respectively receive signals coupled from the power line network and transmit the signals to the corresponding data processing devices to perform attenuation characteristic test and analysis; and a reverse attenuation test is performed: the other test unit transmits a carrier signal to the power line network, and the two test units respectively receive signals coupled from the power line network. The control method has the advantages of being advanced, easy to implement and the like; and the low-voltage power line carrier channel attenuation characteristic test system has the advantages of being flexible to use, convenient to carry, capable of testing bidirectional attenuation and the like.