The present invention discloses a duplexer malfunction detecting method and apparatus, relating to the microwave communication technology field and provided for resolving the problem that the good or bad performance of a duplexer can not be detected online in the prior art. The duplexer malfunction detecting method provided by the embodiment of the present invention includes: receiving the detection wave voltage of the duplexer echo signal; the echo signal is a part of reflection signal which is generated in the duplexer input port by the microwave signal inputted into the duplexer input port; judging whether the detection wave voltage of the echo signal exceeds the reference threshold; if judging that the detection wave voltage of the echo signal exceeds the reference threshold, then determining the duplexer malfunction. By applying the present invention, the online detection of duplexer performance is enabled.
