The invention relates to a conversion method using the gene of hydrolase in a sulfonylurea herbicide as a selection marker. The conversion method comprises the following steps of using a recombinant vector containing a target gene and a gene for encoding the hydrolase in the sulfonylurea herbicide, and converting a host cell; culturing the converted cell obtained in the step in the presence of an ALS (Acetolactate Synthase) inhibitor; using the gene for encoding the hydrolase in the sulfonylurea herbicide as a selective mark, wherein the amino acid sequence of the hydrolase in the sulfonylurea herbicide has an amino acid sequence as shown by SEQ ID NO: 2. According to the conversion method, the idea that the gene of the hydrolase in the sulfonylurea herbicide is used as the selection marker in the conversion process of a plant is proposed for the first time; through two-time screening by selecting agents of different concentrations, the proportion that positive plants are obtained in the later generation of the plant is obviously improved; meanwhile, according to the conversion method, a transgenic plant obtained through the conversion in which the gene of the hydrolase in a sulfonylurea herbicide is used as the selection marker is high in commercial value, good in resistance and further stable in heredity.