Cyanobacteria are an important source of bioactive substances such as phycobiliproteins. It shows a large spectrum of biological activities, for example, antibacterial, antioxidative and in some cases can inhibit human cancer cell-lines1. The main problem is obtaining in the large scale the biomass of the cyanobacteria strains, for its future utilization in process of phycobiliproteins extraction. This determines the scope of this article and necessity of developing of new methods of cyanobacteria cultivation. In this article Nostoc halophilum was cultivated on the nutrient medium BG11 with balanced content of macro and microelements, with supplementation with ethyl ({2-[3-phenylprop-2-en-1ylidene]hydrazinecarbothioyl}amino)acetate in different concentrations, at the first day of experiment. Cultivation of the strain was carried out in 250 ml flasks for 7 and 21 days. Fig. 1 Comparing the results of cultivation of the cyanobacterium Nostoc halophilum with and without supplement, for 7 days From the Fig.1 we can observe that supplementation with ({2-[3-phenylprop-2-en-1ylidene]hydrazinecarbothioyl}amino)acetate increase the growth of Nostoc halophilum in almost 3 times. The same situation was observed in 21 days experiment. In this case we obtained in the flask without supplement – 5,92 g/l of the biomass. In the flask with 5 mg/L supplement – 9,4 g/l of biomass; with 10 mg/L supplement – 7,76 g/l of biomass and with 15 mg/l supplement - 6,1 g/l of biomass. We can see that supplement significantly increased the cyanobacteria cell growth. The optimal concentration of it was found to be at 5 mg/l.