Abstract: The difference in observational performance between different seismological instruments is not easy to find. In this paper, we discuss differences in the performance of observational seismological instruments on the same observation conditions, using a comparison of the probability density functions （PDFs）of the noise power spectrum, based on an analysis of conformance of seismic recorded waveforms. After comparing the probability density distribution of the power spectrum at different frequencies, as well as the distribution and median curves of PDFs of the noise power spectrum, we obtained the quantitative observation difference of different instruments. This difference agrees with the difference of instrument characteristics and transfer functions. By comparing the PDFs of the noise power spectrum, the quantitative and visual differences in the observation performance of different instruments can be given. This is a more detailed view of the difference between instruments and provides a reasonable evaluation of the observation data.