Abstract: The thin-sections of ultramicro structure of Bacillus thuringiensis belonging to 30 subspecies of 23 H-serotypes and 3 straines isolated from the soil were examined by electron microscopy. The result showed that the forming position, the form and the quantity of spore and crystal of the 30 subspecies in sporangium vary from each other. In most of the species, the spore is located on one side of the sporangium and outside of exosporium. The crystal of Bacillus thuringiensis subspecies finitimus is located inside of exosporium. The form of crystal in the sporangium of various subspecies varyes greatly, which is usually dipyramidal, spheroidal, cuboidal or irregular in shape and most of them were single one.In the 3 strains isolated from soil, 87052 strain is similar to H23 (Subsp. japonensis), 85020 and 85040 strains were different from the 30 subspecies.