This research aims to study the efficacy of some chemical additives along with commercial compounds for B. thuringiensis (Agrien) to increase its ability to control the Fall armyworm Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae). Hence, the simi-filed experiment was carried out to investigate the impact of five inorganic salts: Zinc Sulfide (ZnS), Potassium Chloride (KCl), Calcium Oxide (CaO), Sodium Bicarbonate (NaHCO₃) and Potassium Sulfate (K2SO₄) on the potency of Bacillus thuringiensis (Bt) formulation against Spodoptera frugiperda larvae. Three concentrations of each salt (0.1, 0.25 and 0.5%) mixed with the recommended dose of Agrien were assayed against the 2^nd instar larvae of fall armyworm. The obtained results indicated that the Bt+KCl 0.5% recorded the highest corrected mortality percentage (C.M.%) 60.0% followed by Bt formula (Agrien) with 54.67% with no significant differences. On the contrary, the Bt + K₂SO₄ 0.1% treatment gave the lowest (C.M.%) 13.3%. Regarding the effect of the tested compounds on the activities of certain enzymes, its noticed that; the activity of Acetylcholinesterase enzyme (AchE) increased significantly in the 2^nd instar larvae under four treatments; Bt+ZnS 0.25%, Bt+KCl 0.25%, Bt+CaO 0.25%, and Bt+K₂SO₄ 0.25% compared to the control. The activity of (AchE) decreased under the Agrien (92.67 ug AchBr/min/g.b.wt) formula treatment compared to the control (103.3 ug AchBr/min/g.b.wt) with no significant differences. On the other hand, three of the tested compounds significantly inhibited the activity of Acid phosphatase (ACP) compared with the control, Agrien gave the lowest activity (430.67Ux103 /g.b.wt) followed by Bt+KCl 0.25%and Bt+K₂SO₄ 0.25% (675.67 and 754.33 Ux103 /g.b.wt), respectively as compared with the control (810.3 Ux103 /g.b.wt). All treatments resulted in the inhibition of Protease enzyme activity. There were significant differences between the control and all other treatments. Finally, the activity of the Amylase enzyme increased under two treatments, Bt+NaHCO₃ 0.25% (153.33 µg glucose /g.b.wt.) and Bt+K₂SO₄ 0.25% (115.67 µg glucose /g.b.wt.).