Abstract: Objective To appr oach a new method in typing salmonella typhi strains.Method Using 16Sr RNA gene,a high conservative gene in molecular evolution labeled with digoxigenin -11-dUTP by PCR,to investigate the 16Sr RNA gene restriction patterns(16SrRN AGRP)of 40 straits of salmonella typhi after their chromosomes being digested with PstI.Results The PstI 16SrRNA GRP appears obviously polymorphism in strains of distinctive sources.Forty strains can be divided into 14 ribotypes.The fragments containing 16SrRNA gene are sized 4.4kb-29.7kb in 16SrRN AGRP of PstI.Most of RTs have 5-6 tapes.Conclusion The salmonella typhi's long term of prevalence maybe relate to the existance of certain types of RNA in same area.There is always the same RT in the spot of breakout.Analysis of 16SrRNA GRP can be used to trace the infections sources and transmitting routes.