Abstarct: 2,3-dihydro-1,4-phthalazindione (phthalhydrazide), was prepared via the reaction of phthalic anhydride with hydrazine hydrate in ethanole. This compound, which is a monomer, was then reacted with two moles of phenyl isocyanate and the structure of product as a model compound was identified. The structure of the model compound was determined by IR, 1H-NMR spectra. The polymerization of the monomer with stoichiometric amount of various diisocyanates, hexamethylene¬ diisocyanate (HMDI), tolylene ¬diisocyanate (TDI), and isophorane diisocyanate (IPDI), led to new polymers, in high yields and inherent viscosities. Considered products was confirmed by IR, HNMR, thermal gravimetric and analytical elemental analysis. The reaction between Tetrabromo phthalic anhydride and Hydrazin hydrate was produced 4,5,6,7-Tetrabromo-2,3- Dihydro-1,4- phthalazinedion. Then, it reacted with Tolylene diisocyanate in DMAc as solvent. Considered reaction, produced a new polymer with the viscosity of 0.4, that its structure was identified by IR, 1H-NMR, Anlytical and thermal analysis. 1,2-bis-1-ethoxycarbonylmethyl- 2,3-dihydro-1,4-phthalazinedione, was prepared via the reaction of phthalhydrazide and ethylacetate in DMAc. The structure of this monomer was confirmed by IR, 1H-NMR, 1C-NMR.