The invention discloses a method for fast detecting loop-mediated isothermal amplification of African swine fever viruses. An LAMP optimal reaction system is prepared from 25 microliters of matter which comprises l microliter of 8U Bst DNA polymerase, 2.5 microliters of a 10*ThermoPol buffer solution, 6 microliters of 2.5 mM each dNTPs, 4 microliters of 25 mM MgCl2, 1 microliter of outer primers F3 and B3 (5 micrometers), 1 microliter of inner primers FIP and BIP (50 micrometers), 1 microliter of a DNA template, 2.5 microliters of 10M bataine, and the balance ddH2O. An LAMP reaction is performed in a constant-temperature water bath kettle, reaction temperature is 63 DEG C, and reaction time is 45 min. The method is extremely high in specificity and sensitivity, fast, efficient, low in cost, easy and convenient to operate, capable of being effectively applied to fast diagnosis of African swine fever viruses, and applicable to field operation of an animal quarantine institution and a livestock farm.