Biodesalination, using photosynthetic species of bacteria to exclude NaCl ions from seawater could provide sustainable new saline water desalination methods associated with available methods. 90% of salts can be removed by Cyanobacteria and without pressures or external power source. This research aims to isolate and cultivate Cyanobacteria Oscillatoriales (O. sp.) to use in the biodesalination and reduction of total dissolved solids in seawater under the Egyptian condition and use isolated strain at an advanced level which is designing photobioreactor as a stage for biotreatment and use treated water in irrigation. Parameters presented in this paper include the growth rate of (O. sp.), Total Dissolved solids (TDS), pH, Oxidation reduction potential (ORP) and NH4 concentration. The results showed salt reduction ranged from 3 to 4 g.l-1 , and NH4 concentration increased up to 6.5 mg.l-1 and more than 9.99 mg.l-1. The ORP decreased to about 129 mv. This result is achieved from 30 to 40 g of cyanobacteria biomass.