A new series of substituted benzimidazoles (6A-13B) were designed and synthesized using 1-chloro 2, 4 dinitrobenzene and substituted amine by a multi-step synthesis. By using spectroscopic methods and elemental analyses, all the produced substances were identified. All the synthesized compounds were evaluated for in-vitro antimicrobial activity against various human pathogenic microorganisms by employing agar cup plate process using ciprofloxacin as standard drugs. The whole strains of microorganisms were active against every chemical that was generated. Among all these 7B, 12B and 8A are the most active. Because these three compounds show valuable MIC value than other compounds .Structural activity relationship studies showed that compounds with an electron withdrawing. group exhibit enhanced activity, while the other derivatives exhibit moderate activity. Based on the findings, three compounds—7B, 8A, and 12 B—were discovered to be much more active than the other compounds and standard medications in the antimicrobial experiment.