Bacillus thuringiensis (Bt) is a gram-positive spore forming bacteria. It forms a spore in an adverse condition i.e. when nutrients are limited. Bt produces protein crystals in the cytoplasm of the mother cell during sporulation. The protein crystals are insoluble protoxins, when synthesized the ä-endotoxins consist of two multigenic families, Cry and Cyt. Cry proteins are toxic to different insect orders. They are toxic to Lepidoptera, Coleoptera, Hymenoptera, Diptera and also to nematodes.The use of manufactured high toxic pesticides with their harm environmental effect led to search for non-traditional means of control. Musca Domestica plays an important role in the transmission of many pathogens such as cholera, typhoid, trachoma, diarrhea, tuberculosis, salmonella and intestinal sedimentation.The results recorded illustrated the efficiency of Bti bacteria at concentrations (0.5, 1.0, 1.5 and 20%) against the second instar larvae of the domestic fly M. domestica. The results of this study show that the different concentrations of Bti Clearly indicate the percentage of larvae where they increase directly and gradually by increasing the concentration (16, 52 and 80%) of the concentrations used respectively. The results recorded potential effects of the laboratory biocide on the second larval life span of Mucosa domestica. The life span of the mature phase, the number of eggs per female (fertility) and the percentage of hatching, and the number of mutilated individuals were recorded. The results shown that the bacterial pesticide causes a significant decrease in larval life span compared with the control group (10.36±0.027) since the minimum life span is 2.45±0.251 days at concentration of 0.5%, maximum life span is (8.68± 0.158) Days at concentration of 20%.