Leaves of nine kinds of plants from three subfamily of Rosaceae were used as materials. Genetic relationship was analyzed and species were identified through studying FTIR of nine kinds of plants. Leaves mainly contain large amounts of carbohydrates, proteins, lipids, nucleic acids and other substances. The peaks of carbohydrates are mainly between 1　440　and 775 cm-1. The vibration peaks of the cellulose and lignin are between 1　440 and 1　337 cm-1. The peaks between 1　000 and 775 cm-1 are stretching vibration of ribose. The vibration peaks of protein are between 1　620　and 1　235 cm-1. The peak at 1　620 cm-1 is sensitive to CO stretching vibration of protein amide　Ⅰ. The peak at 1　523 cm-1 is assigned to N—H and C—N stretching vibration of protein amide Ⅱ. Peaks of lipids mainly appeared between 2　930 and 1　380 cm-1. The peak at 2　922 cm-1 is CH2 stretching vibration of fat. The peak at 1　732 cm-1 is CO stretching vibration of fatty acids. The mark peak of the nucleic acid appears in the region between 1　250 and 1　000 cm-1. The peak at 1　068 cm-1 is due to the symmetric stretching vibration of PO2－ group of the phosphodiester-deoxyribose backbone, and the peak at 1　246　cm-1 is associated to the asymmetric stretch vibration of PO2－ group. The results showed that the cluster model is established by smoothing, standardizing, the second derivative, principal component analysis and Hierarchical cluster analysis. It is accordant with the traditional classification. The result of cluster shows that Prunus armeniaca L. and Prunus seudocerasus Lindl. were clustered into one (Prunoideae). Potentilla fulgens Wall. Rosa chinensis Jacd and Fragaria ananassa Duchesne var. were clustered into the second (Rosoideae). Pyracantha fortuneana Li, Malus pumila Mill. Eriobotrya bengalensis Hook.f.and Malus hallianna Koehne were clustered into the third (Pomoideae). The correct rate of cluster at subfamily is 100%. The correct rate of cluster at genus is 55.56%.　The correct rate of identification is 100% when unknown species waiting for determined were laid into the model of Hierarchical cluster to identify. This study provides a new thought and method for genetic relationship analysis of planst.