AFIELD experiments were carried out during the winter seasons ….. 2013/2014, 2014/2015 at the Experimental Station Farm of the Faculty of Agriculture, Alexandria University, at Abeis, Alex, governorate, A.R.E. to study the promotive effect of different concentrations of marine algae as biostimulantfertilization and mineral fertilization on growth and yield of Spinach, three of algae were applied in four rates (5%, 10%, 20% and 40%) and sprayed alone or in combination with others and recommended NPK as a control were applied . Plants were harvested after 50 days from planting and the characters were measured such as (plant height (cm), fresh and dry weights of leaves (%), total yield, total leaf's chlorophyll content, mineral contents of leaves and the accumulation of nitrate). All the tested treatments increased plant yield and quality in varying degrees. Ulva lactuca + Bread yeast 5% was the best treatment to increase the yield of Spinach plants in addition was recorded the lowest amount of nitrate in Spinach leaves. We can evaluate the effect of seaweed extract on nitrogen metabolism in root and leaves of Spinach plants cultivated in medium culture deficiency or richened of mineral elements.