Abstract: A highly effective strain of Bacillus thuringiensis, designated as WY 190, was selected from 406 wild strains via bioassay against neonate larva of Spodoptera exigua. Killing test showed that LC₅₀ of original fermentation fluid of the strain was 0.25μl/ml. Serological identification indicated that the strain belonged to H_3a3b type (subsp. kurstaki). TEM observation demonstrated that the stain produced parasporal crystal different in size and forms (including rhombic, small square and elliptic). SDS PAGE electrophoresis indicated the crystal was consisted of two proteins with MW 135kD and 65kD respectively. The strain did not show any other difference in growth, fermentation requirement, and biochemical properties when comparing with commercial strain HD-1.