The invention relates to a kit and detection method for detecting vibrio harveyi by using the loop-mediated isothermal amplification technique. The kit comprises a loop-mediated isothermal amplification reaction solution, a Bst DNA (deoxyribonucleic acid) polymerase and a color-developing agent, wherein the reaction solution contains a reaction buffering solution Thernopol, dNTP (deoxyribonucleotide triphosphate), MgSO4, a forward inter primer (Vh-FIP) TTCGCTTTCGCGAGCCATCTGGTTACCAATTGATCGCCCG, a reverse inter primer (Vh-BIP) ACGCAGAATCAAGCAGTGTGCCGATTTATTCGCCACGACA, a forward outer primer (Vh-F3) CAAAACGGTTCCGAAACGC, a reverse outer primer (Vh-B3) TCGATTCCCCAAGTTTGGAG, a betaine, and sterile distilled water. The detection method comprises the following steps: extracting bacterium DNAs, carrying out loop-mediated isothermal amplification, carrying out color-developing detection and the like. By designing the primers according to the vibrio harveyi toxR gene conservation area and detecting by using the LAMP (loop-mediated isothermal amplification) technique, the invention achieves high specificity and high sensitivity; the kit has the advantages of high detection speed, high accuracy, excellent sensitivity, convenient on-site application and the like; and the defects of long cycle, low sensitivity, high cost, difficult on-site application and the like in the prior art are solved.