This research aim to study the effect of some factors (concentration of insecticide, temperature and pH levels) affecting biodegradation of insecticides by cyanobacteria. The superior isolates out of twelve cyanobacterial isolates, which isolated from soil contaminated with insecticides were Nostoc muscorum and Anabaena oryzae. Results indicated that an increase in dry weight and N2 fixation was recorded with increasing chlorpyrifos concentration from 0 up to150 ppm. These results were noted with Anabaena oryzae. On the other hand, there was an increase in the average of dry weight and N2 fixation with increasing the concentration of carbofuran from zero up to 80 ppm. The highest nitrogen content was recorded in Nostoc muscorum. The biodegradation of the pesticide (chlorpyrifos and carbofuran in liquid cultures) by cyanobacterial isolates was evidenced by complete discoloration of cyanobacterial growth at 12 days of incubation. The fixed nitrogen and dry weight of Anabaena oryzae and Nostoc muscorum grown at different concentrations of chlorpyrifos (0, 50, 100, 150 and 200) and different temperature degrees (20,25,30 and 35°C) as well as different pH levels (5, 6, 7 and 8) were determined. Results indicated that the maximum uptake of chlorpyrifos by Anabaena oryzae and Nostoc muscorum was recorded at 30°C and pH 7.0. Moreover, the maximum removal of carbofuran by Anabaena oryzae and Nostoc muscorum at different concentrations (0, 40, 80 and 120) was recorded at 25°C and pH 7.0