Pseudomonas pseudoalcaligenes insecticidal protein was isolated and purified sucessfully. Amino acid composition analysis showed that it is an acid protein. Laser Raman spectra of the insecticidal protein have been obtained and analysed.It is found that protein of the sample contains predominantly β-sheet content.The majority of tyrosyl residues are exposed and a few are buried in the protein of the sample.The sample has trans-gauche-trans configuration of C—C—S—S—C—C linkage.