A Bacillus thuringiensis isolate (KIII), isolated from Egyptian soil, was produced in liquid culture using yeast extractmolt- glucose medium, where the spore-crystal complexes were recovered. The complexes were formulated into three granule formulations, then the toxicity of the isolate was evaluated in laboratory by bioassay against the cotton leafworm S. littoralis. Results exhibited that, the best formulation for keeping biological activity (both efficacy and survival) of B. thuringiensis was the alginate granules. Bioassays of the formulation containing Congo red (as UV- protectant), indicate the superiority of this additive to other in improving the effectiveness of B.t. under exposure to sunlight. Also, adding molasses + soybean flour exhibited the highest efficacy when using as feeding stimulants. Zinc sulphate also showed a remarkable effect in enhancing B.t. potency and viability.