Scorpion venoms contain of variety of peptides toxic to mammals ، insects and crustaceans. Toxic peptides are the main factors in scorpion venom causing toxicity, (their amount being 1-3%of total venom.). Most of the scorpion toxins have been isolated from the venoms of scorpions in the family Buthidae. The scorpion Buthotus Schach belonging to the Buthidae family is widely found in the western region of Iran , but no published articles has been found to date on its venoms. Therefore in this study, we aimed to isolate and purify mammalian toxins from the venom of the scorpion Buthotus Schach present in Iran . For this study the crude venom was dialyzed against deionized water for 48 hrs., and centrifuged in order to separate soluble proteins from the insoluble mucoproteins and the soluble proteins was applied on a sephadex G-50 gel filtration. The toxicity of each fraction was determined by I.V injection to mice and toxic fractions were further purified by two steps ion-exchange (anion) and RP-HPLC chromatography. The purity of the final toxic protein fractions was checked and confirmed by RP-HPLC column & SDS-PAGE. Finally two neurotoxin s , termed BS311 and BS313 were purified. Results in this study showed that the LD50 of crude venom on mice is 84µg/mice and contain at least 20 peptides from high molecular weight to low molecular weight out of which two of the peptides which showed toxicity to mice were isolated and purified. LD50 of these toxins were determined to be 3 and 2.17µg/mice respectively. The molecular weight of the purified toxins BS311 and BS313 were 7860and 7600 Da, respectively, as determined by SDS-PAGE. In conclusion this study showed that the main factor in the toxicity of scorpion (Buthotus Schach) venom is low molecular weight peptides.