Vascular wilt of tomato caused by Fusarium oxysporum f.sp. lycopersici is considered as one of the most important diseases of this plant worldwide. In East Azerbaijan province also, Fusarium wilt causes the greatest damage to the tomato yield. This research was conducted to evaluate the influence of antagonistic bacterium Bacillus methylotrophicus and Carbendazim fungicide on causal agent of disease in laboratory conditions, also in current study, the effect of Carbendazim on bacterial population was studied using spectrophotometer at 12, 24, 72, 96 and 120 hours after culturing to determine the synergistic or inhibitory effect of Carbendazim on B. methylotrophicus, when biological and chemical control are integrated together. ccording to the results, the inhibitory effect on radial growth of pathogen mycelium in dual culture test was measured at 54% in compare to control treatment. Antagonistic bacterium also made an inhibition zone with average diameter of 7 millimeter around the colony of fungus. When mixed with the culture medium, Carbendazim inhibited radial growth of mycelium by only 25% at its lowest concentration of 62/5 ppm, but in the concentrations of 250 to 2000 ppm, stopped growth of mycelium completely. Fungicide did not show any inhibitory effect on conidial germination at all applied concentrations and germination was observed at 100% in all treatments. In the culture medium, Carbendazim showed the synergistic effect on the antagonistic bacterium so that 96 hours after culturing, the bacterial population reached its highest level in liquid medium containing different concentrations of fungicide and their difference with control treatment was significant. Among the different concentrations of this fungicide, the recommended concentration in the field application (2000 ppm of WP formulation) had the greatest impact on increasing population of B. methylotrophicus.