The full length cry2Ab gene was cloned by PCR-RFLP method from Bt strain B-Pr-88, which was isolated in China with high toxicity to the Lepidopteran insect pests. Nucleic acid sequence analysis showed that this gene was 1902 base pairs encoding 633 amino acids. This cry gene was named cry2Ab4 as a novel gene by Bacillus thuringiensis Delta Endotoxin Nomenclature Committee. The full open reading frame sequence of the cry2Ab4 gene was amplified with a pair of PCR primers L2ab5/L2ab3 designed according to its DNA sequence,and inserted into the BamH I /EcoR I sites of E. coli expression vector pET21b to obtain the recombinant plasmid pET-2Ab4. The result of SDS-PAGE proved that Cry2Ab4 could be expressed as a 60 kD protein in E. coli BL21 (DE3)strain induced by IPTG. Bioassay of the expressed product of the cry2Ab4 gene showed that Cry2Ab4 was highly toxic to the larvae of Helicoverpa armigera and Leguminivora glycinivorella, moderately active to the larvae of Plutella xylostella and Chilo suppressalis, but not insecticidal to the larvae of Spodotera exigua and Ostrinia furnacalis. Our result indicated that cry2Ab4 gene could be used as a novel gene for generation of transgenic plants and engineered microorganism.