10 pieces of yellowish green peridot from Jilin province with fine and pure texture were selected to analyze the relationship between frequency drift in middle-infrared band and color appearance, through the replacement of Fe2+. The actual crystal chemical formula of the samples calculated by Oxygen atom method is: (Mg1.84,Fe0.19)2.04[(Si0.982,Al0.001)0.983O4], so prove that it is chrysolite  and the replacement of Fe2+ and Mg2+ in the position M, which led to the yellowish green appearance. With the help of Fourier infrared spectrometer TENSOR27 and One Way ANOVA analysis study the infrared spectra of 10 samples and analyze the impact Fe2+ had on frequency drift, getting the Correlation coefficient r between Fe2+ and the wave-number near 1040cm-1, 622cm-1, 522cm-1, and the value of r are -0.896,-0.884,-0.903, therefore, with Fe2+ increasing ,three reflection peaks drift to the lower frequency. Compare the reflectivity in the visible area (360nm ~ 750nm) tested by colorimeter Color i5 with the mafic peridot end of forsterite solid solution, finding that with the reflectance peaks drift to low frequency, reflection of blue and purple light decrease, blue and purple tone in peridot decreasing; reflection of the red and orange light increases, red and orange tone increasing. It is concluded that in the transformation of mafic Peridot end to chrysolite peridot end, reflection peaks in infrared band drift to lower frequency, causing the increase of red and orange tone, decrease of blue and purple tone in Peridot.