Recently, many genes responsible for genetic diseases have been identified and abnormal genes could be analyzed using southern hybridization and PCR techniques. However southern hybridization method is time consuming, takes too much labor, uses isotope and there are cost problems. PCR techniques has been difficult to amplify target genes which are greater than 5 kb. Nowadays, a new method was developed for effective amplification of longer DNA. It`s called LA-PCR. This method is used to amplify up to 22 kb of human gDNA. Therefore, in the case of diagnosis for facioscapulohumeral muscular dystrophy (FSHD), it is more difficult to analyze the abnormal gene because of extremely GC rich and highly repeated region on FSHD gene. In this study, we developed the new technique for the analysis of FSHD gene using modified LA-PCR. The probes p13E-11 and pFR-1 detect DNA rearrangements associated with FSHD as under 28 kb DNA fragment in genomic southern analysis digested with EcoR1 and the fragment contains 3.3 kb KpnI tandem repeats (73% GC). This kind of DNA could not amplify usually but amplified the tandem repeats region up to 15 kb (4 repeats) using LA PCR modified by 7-deaza dGTP. It may be useful for the diagnosis of triple repeats extension diseases (Fragile-X, DRPLA, Myotonic dystrophy, Huntington disease, etc.) and large fragment amplification of GC rich and/or tandem repeat region.