The clinical appearances of human Leishmaniases implicate a wide spectrum of simple cutaneous self-healing (Cutaneous Leishmaniasis) to a visceral (Visceral Leishmaniasis) disease where the parasites are outbreak into the reticuloendothelial system with a fatal outcome. It is wide range, worldwide, without drug, vaccine, secticide and has not sterile immunity and Efforts in this field has not been successful. Research on efficacy of medicinal plants, is including the research infrastructure. Herbaceous plants tomentose perennial local name Khouchoobe in Kerman and official Zangoolaei Looleh baric and scientific name Onosma stenosiphon "Traditionally in the past as a poultice to treat skin, superficial cuts, wounds and acne has been used . It is disinfectant properties at the site of the wound has been proved. Purpose of this was in vitro antileishmanial activity of Onosma stenosiphon extract against Leishmania major. Sufficient root of Onosma stenosiphon were minced, sterilized and prepared as tropica with concentration of 0.8, 4 and 20 and 100 μg. Leishmania major [MRHO/IR/75/ER] Amastigote was isolated from mice spleens and then transformed to promastigotes in Novy-Nicolle-Mac Neal (NNN) medium , then RPMI1640 and supplemented with penicillin (100 U/ml), streptomycin (100μg/ml) and 20% heat-inactivated fetal calf serum (FCS) at 25°C. A fixed initial density of the parasites (both, Logarithmic and Stationary phases) was transferred to screwcapped vials containing 5 ml of RPMI1640 media to which different concentrations of 0.8, 4, 20 and 100 μg OSE were added and each concentration was done in triplicates. Each run also included control. The mortality of parasitoids was measured by the enzyme-linked assay (ELISA) methods. The percentage viability of OSE and stationary and logarithmic phases of Leishmania major [MRHO/IR/75/ER] showed that viability of parasites in PMs significantly decreased in NSE 0.8, 4, 20 and 100 μg treatment compare to control group (P<0.05). As shown, after 48hour, the percentage inhibition of OSE and stationary and logarithmic phases of Leishmania major [MRHO/IR/75/ER] that the percent inhibition is density in time (P<0.05). According to the results, OSE is effect in inhibiting and the duration of exposure and concentration correlates with inhibition.