The invention discloses an on-site rapid detection method and kit for detecting ASFV based on a CRISPR / Cas system. According to the method, the specificity of crRNA is utilized to effectively guarantee the accuracy of nucleic acid detection of a virus characteristic sequence, whether or not the ASFV exists in a sample can be determined through test paper or fluorescence within 1-2 hours at normaltemperature, and the accuracy is improved somewhat compared with the accuracy of a traditional PCR-based detection method. By adopting the method and the kit, the ASFV can be conveniently and quicklydetected on site, such as a pig farm and a slaughterhouse, complex temperature control instruments such as a PCR instrument and a centrifuge are not needed, an observable result can be quickly obtained only by a constant temperature device and a simple fluorescence detection device, and if a lateral flow test paper color development scheme is used, macroscopic on-site detection without instrumentscan be even achieved, so that the health condition of the pig farm can be known more efficiently, and loss is avoided; the lower-cost, faster and more convenient detection method is provided for ASFVdetection.