A series of 2-amino-5-(substituted phenyl) 1,3,4- thiadiazol have been synthesized through the reaction of  thiosemicarbazide with substituted  benzoic acids in the presence of phosphoroxy chloride readily undergo  nucleophilic addition – elimination reaction with chloroacetyl chloride in benzene as a solvent to afford 2-chloro acetamido compounds. The prepared compounds were subjected  cyclization reaction and results in the formation of a series of 2- imino-3-(substituted phenyl)  1,3,4- thiadiazol-2yl-thiazolidinone -4 one .  The IR ,1H and 13C- NMR spectra of the prepared compounds were confirmed to their proposed structures . Finally antimicrobial activity of the newly obtained compounds were tested against Klepsilla pneumonia (gram -ve )     and  Staphylococcusaurous (gram + ve)  and the results showed that most of the prepared compounds are sensitive against both types of test organisms in different activities .