Abstract: An application of an OBF1 transcription factor in chromosome doubling of a plant and a transgenic plant cultivation method are provided. The gene sequence of the OBF1 transcription factor is shown in SEQ ID NO: 1; and the plant includes petunias, tomatoes, and tobaccoes. An OBF1 gene is introduced into plant cells or tissues, and under treatment with kanamycin, a chromosome-doubled transgenic cell line or plant is obtained; and the transgenic plant grows vigorously and exhibits resistance to biotic stress. After treatment according to the present invention, plants still easily self-pollinate, thus enabling efficient separation of doubled offspring plants, and the doubling trait can be stably inherited.