The present invention discloses a method and a device for detecting a signal power, and belongs to the field of communications. The method includes: when a receiver converts a received receive signal and outputs an output signal, separating a direct current signal and an alternating current signal from the output signal; converting the direct current signal into a first analog voltage signal; converting the alternating current signal into a second analog voltage signal through a transimpedance amplifier TIA; and obtaining a power of the receive signal according to the first analog voltage signal and the second analog voltage signal. The device includes: a first separating module, a first converting module, and an obtaining module. The present invention can improve accuracy of detecting a signal power.