The invention discloses a method for preparing a promoter (PBnPABP2) of Brassica napus BnPABP2 and the application thereof. The operation of cloning a PBnPABP2 sequence by using a genome walking method comprises the following steps: extracting genome DNA by using a SDS cracking process; in different systems, carrying out restriction endonuclease reaction on the extracted DNA respectively by using endonucleases DraI, EcoRV, PvuII and StuI; after the obtained DNA is connected with a linker fragment, carrying out first-round PCR amplification by taking the linker fragment as a template; and carrying out second-round PCR amplification by taking a50-time diluent of the obtained first-round PCR product as a template, thereby obtaining the PBnPABP2. The PBnPABP2 is applied in the roots, stems, leaves, flower buds, anthers and peels of plants. The promoter has the function of driving the expression of exogenous genes, and the expression sites thereof are respectively in the roots, stems, leaves, flower buds, anthers and peels of plants; and the promoter has application potentials in the aspect of safety of edible oil of Brassica napus and the aspects of improving the disease resistance, stress resistance and lodging resistance of crops, improving the quality of crops, artificially creating a male sterile line and a restoring line, enriching germ plasm resources, and the like through transgenosis.