The invention discloses a low voltage power line carrier communication signal modulation mode identification device comprising a sample unit, a signal pre-processing unit, an input vector forming unit and a determination unit; the signal pre-processing unit pre-processes a modulation signal so as to obtain source information; the input vector forming unit extracts feature parameters contained in the source information, and a feature parameter matrix formed by the feature parameters serves as an input vector of a nerve network; a nerve network algorithm identifies a modulation mode corresponding to the modulation signal. In addition, the invention also provides a system comprising the low voltage power line carrier communication signal modulation mode identification device.