Identification of plant species is one of the clues, which is an important tool in criminal investigation. However, morphological test and DNA extraction are very difficult in minute plant pieces. Thus, it is necessary to develop a technique for classification and identification based on biological and chemical components, which does not require DNA analysis. This study analyzed the lignin of the cell wall components, which are products of secondary metabolism of a plant and also examined the species peculiarity and utility in forensic science. An analysis method of lignin is Pyrolysis-Gas chromatography (Py-GC). Analysis of trace amounts of dried plant samples using Py-GC shows results in waveform data, called pyrogram. Powdered samples each of 1.4 mg were dried, in all 22 plant species including Gramineae and Leguminosae were used for Py-GC. Thirteen characteristic peaks were chosen among a pyrogram of Gramineaes and it was converted into a bar graph and compared with other plant species. As a result, same plant species showed the similar pattern, and the same plant that was taken from a different place also showed the same pattern, and reproduction characteristics were recognized. Therefore, the possibility that difference in plant species is specific was shown by the pyrogram pattern. Even if it was the sample, in which DNA cannot be extracted, as for this method, a classification of a plant species was possible. Preprocessing of a sample is simple, as it has to only be dried. In conclusion, the application of this method in criminal investigation will involve swiftness and also forms a simple classification method for plant species.