The invention discloses a detecting method capable of preventing electromagnetic interference of a card reader. The method includes the following steps: generating an original magnetic stripe signal; synthesizing an interferenced magnetic stripe signal; the interferenced magnetic stripe signal being synthesized by the original magnetic stripe signal and an interference signal of a to-be-detected electromagnetic source; decoding the interferenced magnetic stripe signal to obtain decoding parameters; determining whether original magnetic stripe parameters corresponding of the original magnetic stripe signal is consistent with the decoding parameters; if the consistency is determined, then the detection result is that the electromagnetic interference source can not meet requirements of a magnetic card reading apparatus for electromagnetic interference, and if the consistency is not determined, the detection result is that the electromagnetic interference source can meet requirements of the magnetic card reading apparatus for electromagnetic interference. The invention also discloses a detecting device capable of preventing electromagnetic interference of the card reader. The embodiments of the invention can accurately detect whether the electromagnetic interference source meet requirements of the magnetic card reading apparatus for electromagnetic interference, increase safety of the magnetic card reading apparatus and prevent magnetic card information from being read.