The invention provides a mitochondrial T3866C detection kit of Leber disease, and an application thereof. The detection kit is composed of a DNA extraction mixed solution, a PCR mixed solution used for amplifying T3866C, outer primers and inner primers designed aiming at T3866C, a restriction endonuclease Bgl II, a positive control, and a negative control. According to the invention, genomic DNA is rapidly extracted from small amounts of samples such as blood samples, hair with follicle, oral mucosa smears, or saliva. Therefore, a problem of DNA extraction in primary Leber disease patient blood of traditional methods is solved, pain of patient to be detected is reduced, a problem of cross-region sample transferring is solved, enzyme digestion specificity is improved, false negative is avoided, and detection result stability is improved. The kit provided by the invention is rapid, simple, accurate, and economical. With the kit, primary-Leber-disease-related mtDNAT3866C mutation large-scale screening and preventive inspection can be implemented.