A method of manufacturing a reference material for determining incorporation of a genetically modified (GM) plant into a sample or analyzing a mixing ratio from a tissue-cultured cell line that is obtained by incubating tissues of either a GM plant or a non-GM plant, and a method of determining incorporation of a GM plant into a sample and analyzing a mixing ratio using the reference material are provided. The reference material for determining the incorporation of a genetically modified (GM) plant a sample or analyzing a mixing ratio using the tissue-cultured cell lines that are obtained by incubating tissues of the GM plant and the non-GM plant can be useful in producing a countless number of populations having the same genetic traits via the tissue culture. Thus, when a culture capacity of the reference material is increased to a large volume, it is possible to obtain a large volume of the reference material having uniform qualities with no quality variation between batches. Unlike the conventional reference materials manufactured using grain powder, a reference material with 100% purity can be obtained as either a GM or non-GM reference material by verifying the purity of the tissue-cultured cell line. Accordingly, it is possible to provide the uniform and stable supply of a reference material having uniform compositions.