The invention provides a nonlinear detecting method of a 
repeater power 
amplifier. The method can monitor a nonlinearity and digital pre-
distortion rectifying result of the power 
amplifier and judge whether the result is reasonable or not by virtue of a three-order 
intermodulation valve of a double-tone 
signal, and the method comprises the following steps: 
signal preprocessing, FFT simplifying after determination of resolution ratio and 
intermodulation calculation. Besides a 
repeater, the nonlinear detecting method is also applicable to a plurality of 
wireless communication systems comprising a large-power power 
amplifier. The nonlinear detecting method has the beneficial effects that the 
intermodulation simplifying detecting 
algorithm complexity in the numeric field is low, the operating rate is quick, the implementability is achieved, an instrument is not required by the 
algorithm, nonlinearity degree of the power amplifier can be monitored visually by a 
repeater system, and the 
linearity rectifying degree of the power amplifier can be monitored by a digital pre-
distortion algorithm simultaneously. By utilizing the nonlinear detecting method, the intermodulation magnitude can be calculated conveniently, the 
algorithm complexity is low, the source consumption is less, the method is easy to realize, and the stability of the repeater 
system and the digital pre-
distortion algorithm is improved simultaneously.