Abstract:Leptospirosis is a severe zoonosis in the world.The methods for detecting leptospira are not sensitive and specific so far,The problems in early diagnosis for leptospirosis remain unsolved.According to the sequence of the DNA specific fragment from RGA strain,the pair of polymerase chain reaction(PCR) oligonucleolide primers were synthesized,named primers G1,G2.PCRs were carried out with these primers for detecting the microquantity of various serovars,serogroups of leptospira. All the DNA of Leptospira interrogans could be amplified by primers G1,G2 and the DNA of Leptospira biflexa and other bacterum had no amplification at all.The samples obtaining 5 pg DNA could give a positive result in the PCR assay by agarose gel electrophresis and obtaining 5 fg DNA by DIG probe hybridization. Detecting sera from early leptospirosis patients by PCR,positive rate was 82% and much more sensitive than by MAT and dotELISA;The results demonstrated that PCR was a very sensitive and specific technique of DNA Amplification,which could be used as a powerful tool in the early diagnosis and epidemiological investiga-tion of leptospirosis.