African swine fever virus (ASFV) is a kind of DNA virus and can infect both domestic pigs and wild boars with fatality up to 100%. The contaminated meat products mainly led to the worldwide transmission of ASFV. The outbreak of ASF greatly affects the supply stability of meat products as well as the development of the global pig industry. In this study, a visual isothermal amplification detection assay for ASFV based on trimeric G-quadruplex cis-cleavage activity of Cas12a was developed. The introduction of Cas12a could discriminate the specific amplification from the non-specific amplification and improve the sensitivity. The detection limit was as low as 0.23 copies/μL. This assay had good potential in the detection of ASFV and would be helpful for the stability of meat production and supply.