Some aspects on the application of second order diffraction of a monochrometer in laboratory EXAFS measurement are studied. Significant distortions in measured X-ray absorption fine structure occur when there are impurities' emission lines on the continuum spectra m the investigated energy range. A method for correcting that distortion is proposed. As the EXAFS amplitude decreases, which is caused by the application of second order diffraction of a monochrometer, how to obtain correct structural parameters is also discussed.