The invention relates to a detection kit for isothermal amplification of nucleic acid for the white spot syndrome virus and a detecting method thereof. The kit is designed by using a set of LAMP primers as the main body designed according to the gene conserved sequence of the white spot syndrome virus. The kit is provided with eleven agents needed by WSSV detection including SEMP lapping liquid, nucleic acid extract, UNG enzyme, TE buffer solution, enzymolysis buffer solution, LAMP reaction solution and on the like, thus realizing a programmed and standardized detection; therefore, the invention has the advantages of the highest sensitivity, simplicity, rapidity, safety, good specificity and low cost, and the amount of the copies detected with virus can be as low as 26. Only one water-bath is needed to correctly detect the white spot syndrome virus in prawns and aquaculture water within 2 hours by the kit and the detecting method. Moreover, the problem that the detection is subject to interference in the LAMP technology is also solved. The detecting method of the invention is expected to substitute the previous related detecting methods of the white spot syndrome virus, such as the electron microscope method, the TE staining method, the biopsy method, the antibody detecting method, the nucleic acid probe hybridization method and the PCR detecting method.