NOVELTY - Method for preparing pesticidal protein, involves (a) designing primer having CpGVorf13 sequence at 94th position, (b) performing PCR amplification on brachytmema segment having 663 base pair using CpGV gene DNA as template, (c) identifying PCR product by agarose gel electrophoresis, (d) extracting pT-Cp12 plasmid, and subcloning segment to an expression carrier pET-28a to obtain pET-28a-Cp13, (e) transferring Escherichia coli DH5 alpha to the pET-28a-Cp13, (f) transferring the identified plasmid to E.coli BL21, and (g) centrifuging the sample.    USE - The method is useful for preparing protein for improving pesticidal activity of beet armyworm nuclear polyhedrosis virus medicine, Plusia agnata nuclear polyhedrosis virus medicine, Bacillus thuringiensis Bt C-33 medicine or Bt YH-8A medicine.    ADVANTAGE - The prepared protein has excellent synergistic effect, convenient to use, environmentally-friendly and causes no side effects.    DETAILED DESCRIPTION - Method for preparing pesticidal protein, involves (a) designing primer having CpGVorf13 sequence94th position, where the primers are upstream primer: 1:5'-cgcggatccatgccgttggcgagacagcg-3' (P1), and downstream primer: 1:5'-cccaagctt ctacaaatcacttttcgtttgctt-3' (P2), (b) performing PCR amplification on brachytmema segment having 663 base pair using CpGV gene DNA as template, subjecting the obtained fragment to pre-modification at 94 degrees C for 5 minutes, repeating pre-modification process for 30 times, and extending the fragment at 72 degrees C for 10 minutes, (c) identifying PCR product by agarose gel electrophoresis (0.8 wt.%), recycling PCR product by PCR recycling purifying reagent kiln, connecting the PCR product with pMD18-T carrier, transferring Escherichia coli DH5 alpha to connected product, inoculating vitiligo into 5 ml of lysogeny broth (LB) culture medium and maintaining the inoculated medium overnight, (d) extracting pT-Cp12 plasmid, identifying positive clone using enzyme cut, measuring sequence, recycling target segment, and subcloning the target segment to an expression carrier pET-28a to obtain pET-28a-Cp13, (e) tranferring E.coli DH5 alpha to the pET-28a-Cp13, uniformly coating trans-injected bacteria to a selective Linda A. Anderson (LA) panel, inverting and culturing the panel at 37 degrees C for 14 hours, inoculating clone into 5 ml of LA culture medium containing relative antibiotics, vibrating the medium overnight, extracting plasmid and identifying the extracted plasmid using enzyme cut, (f) transferring the identified plasmid to E.coli BL21, uniformly coating trans-injected bacteria onto a selective LA panel, inverting and culturing the panel at 37 degrees C for 14 hours, inoculating single bacteria into 5 ml of liquid LB culture medium, maintaining the inoculated bacteria overnight at 37 degrees C, transferring 1% of culture into 5 ml of fresh liquid LB culture medium, culturing the transferred bacteria at 37 degrees C till OD600 is 0.6, adding isopropyl- beta -D-thio-galactoside (IPTG) (1 mN) to the cultured bacteria, inducing the culture by segmental hollow carrier pET-28a without target segment for 6 hours, and sampling the induced medium to obtain negative reference, and (g) centrifuging the sample, collecting bacteria from the centrifuged sample, suspending the collected bacteria in phosphate buffered solution, and detecting the suspended bacteria using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) to obtain Cp13 protein.