The invention provides a 
CRISPR / Cas12a one-step 
nucleic acid detection method. The method comprises the following steps of 1, selecting a target sequence of 
bacteria to be detected, designing upstream and downstream primers of RPA, performing specific screening, amplifying the target sequence to obtain a primer 
amplicon sequence, and performing specific 
verification on the primer 
amplicon sequence by utilizing NCBI BLAST; 2, designing specific crRNA; 3, designing a single-stranded 
DNA reporter molecule; 4, mixing the single-stranded 
DNA reporter molecule, the RPA upstream and downstream primers, freeze-dried RPA reaction particles, 
magnesium acetate, an RPA hydration 
buffer solution, NEB buffer 2.1, RNase Inhibitor and a target to be detected to obtain a reaction mixture; 5, constructing a one-
step detection kit comprising a reactant placing tube and an 
injector, placing the reaction mixture at the bottom of the reactant placing tube, and preloading crRNA and Cas12a 
protein into the 
injector; and 6, after the reaction mixture reacts, pushing a 
piston of the 
injector to enable the crRNA and the Cas12a 
protein to be mixed with the reaction mixture for a reaction, and performing 
blue light excitation to obtain a detection result.