In the present study, 27 primers were screened under different cycles by random amplified polymorphic DNA (RAPD) method. Mathematical models were used for analysis of the genetic relationships among strains, including vaccinal, reference strains and nine field isolates previously characterized as Mycoplasma gallisepticum (MG)F by RAPD and pulsed field gel electrophoresis (PFGE). The PFGE was considered as laborious, expensive and time-consuming than RAPD method. These methods improved the typeability for epidemiological studies of MG with regard to differentiation from vaccinal and field strains.