Two CMS genes were truncated in different lengths，expressed in prokaryotic cells and genetically transformed in Arabidopsis thaliana and Brassica napus. to determine the relationship between the toxicity of the protein encoded by the ogu CMS sterility gene orf138 and male sterility and the core functional region of the hau CMS sterility gene orf288. The results of truncated male sterile gene orf138 showed that the growth of E. coli expressing pET32a^1-138 and pET32a^1-93 containing transmembrane helix was significantly inhibited after the IPTG was added，while the growth of E. coli expressing pET32a^45-138 without transmembrane helix was not affected. It is indicated that the toxic region of ORF138 is located at the N-end containing the transmembrane helix. Results of genetic transformation showed that PS：Rfp138^35-138 and PS：Rfp138^45-138 did not cause male sterility in Arabidopsis thaliana and B. napus，indicating that the complete N end is necessary for ORF138 to induce male sterility in plants. The results of genetic transformation of different truncated orf288 in Arabidopsis thaliana showed that positive seedlings transformed with PS：Rfp288^104-288，PS：Rfp288^134-288 and PS：Rfp288^164-288 were male sterile，while all the positive seedlings transformed with PS：Rfp288^194-288 were fertile. It is preliminarily proved that the core functional region of orf288 is orf288^164-288，indicating that the 164th-194th aa of ORF288 may be closely related to the cytoplasmic male sterility in hau.