Using Fourier transform infrared (FTIR) spectroscopy of three willow leaf and leaf disease, the young leaves of the same branch and leaves, yellow leaves, leaf disease spectrum testing, aims to analyze the willow leaf disease of some physiological changes, to explore the effect of disease leaves on the clustering of the system. Infrared spectroscopy blade at different stages of major change in 1800~ 800 cm-1, this bands second derivative processing, you can clearly see the superimposed region of the protein and lignin 1700 ~ 1500 cm-1, characteristic peaks of calcium oxalate 1621,1318 cm-1, characteristic peaks carbohydrate peak near 1075 cm-1 strong there are significant changes, with absorbance ratio A1621 / A3390, A1318 / A3390, A1075 / A3390 to compare the relative content of calcium oxalate and sugar, with 1700 ~ 1500 cm-1 band fitting peak area ratio S amide I /S lignin, S amideⅡ/S lignin and S amideⅡ/S amide I used to compare the relative amounts of the protein. The results showed that the relative contents of calcium oxalate in the diseased leaves were increased, and the relative contents of polysaccharide and protein decreased. The blade 1800 ~ 800 cm-1 range of the second derivative of systematic cluster found diseased leaves change did not affect the chemical composition of the clustering effect, clustering correct rate of 100%.