The exploitation of Spirulina platensis as bio-stimulator for organic-farming systems was studied. Mass production of Spirulina platensis biomass was done in polethylene transparent containers (1000 LTRS. capacity) under continuous aeration, at 30 C, pH9. 00 and replacement of Na+ salts by K+(13 g/L) in the standard medium was more effective for production of bio-stimulator yield. Chemical analysis of Spirulina platensis bio-stimulator revealed that it contains: 6.7% N, 2.47% P and 2.14% K as well as adequate amounts of minor elements needed for plant nutrition. It was found that cultivation of Spirulina platensis in the modified medium increased its nitrogen and potassium level ten and sixteen times respectively compared to standard medium. Lead was totally absent in Spirulina platensis biomass in either standard or modified medium. The bioreactor design was modified to reduce the composting process time. Recorded results for Spirulina platensis application as biostimulator revealed that the yield of pepper inoculated with bio-stimulator is recommend than that of NPK.