Isolation of cyanobacteria dominated in the soil samples collected from different sites in Kafr El- Sheikh, and El-Dkahlia governorates isolates were successfully obtained as bacterial free cyanobacteria. They were identified cyanobacteria was carried out using the following: thallus color, thallus morphology and size of heterocyst, vegetative and reproductive cells. Heterocyst-forming cyanobacteria were also cultured as Anabaena sp., Nostoc sp., Oscillatoria sp., and Chroococcus sp. Nostoc sp . were isolated at high frequency; Nostoc sp. and  Anabaena sp. isolates representing in kafr El-Sheikh and El-Dakahlia Governorates. Less frequency of cyanobacteria belonging to different genera namely Oscillatoria sp. and Chroococcus sp. Nostoc spp.were recorded highest amount of fixed nitrogen and mass production with in increasing incubation period of interacellular and /or extracellular nitrogenfixation. While,the most active strains for nitrogenase activity were Nostoc mucorum K and Anabaena oryzae D.