Abstract: Power meters, oscilloscopes, detectors, and vector network analyzers are commonly used in microwave measurements. The introduced errors by these instruments have direct impact on the measurement accuracy. In this paper, the measurement methods of power meters, oscilloscopes, detectors, and network analyzers are described, based on which the introduced errors by the typical measurement instruments under different measurement conditions are analyzed. The experiment results demonstrate that the measured power by the detectors is at most 0.4 dB bigger than that by the oscilloscope. The maximum difference of the measured power by the oscilloscope under different suppression bandwidths is 0.3 dB. The measured power by the vector network analyzer N9917A is 1 dB bigger than that by the analyzer AV3672 at 4 GHz with the attenuation of 60 dB.