The invention provides a multichannel analyzer for use in a multichannel spectrometer, which comprises a standard spectrum calibrator for obtaining energy calibration parameters of said multichannel spectrometer; an environment background spectrum calibrator for obtaining parameters of a current and a previous environment background spectrum; a peak shift detector for analyzing the parameters of the current and previous environment background spectrum to determine whether a peak shift occurs between them and to determine a correction coefficient of the peak shift; and a parameter corrector for correcting the energy calibration parameters of said multichannel spectrometer using said peak shift correction coefficient. The invention also provides a method for correcting a peak shift of a multichannel spectrometer adapted in the multichannel analyzer. The method for correcting and the multichannel analyzer can correct and monitor the peak shift of the multichannel spectrometer in real time.