This study employs corpus analytical tools to carry out a systematic study on Chinese Science and Engineering Majors' (SEMs') use of self-repair in their oral English. The study aims to find out the overall feature of using self-repair by SEMs and to see if there exists statistically significant difference of using self-repair across different English proficiency level groups. Results show that SEMs use self-repair frequently and they use same information repair (SIR) most. There is no statistically significant difference in the overall frequency of using self-repair among SEMs' levels. SEMs' correction rate is rather low. Self-monitor theory and communication strategies theory are used to explain the results. At the end of the thesis, the author provides some suggestions for oral English teaching