Abstract: Three methods of high temperature steam sterilization, centrifugal degerming and filtration sterilization are used to investigate different changes of corrosion extent in Shengli Oilfield Ninghai area reinjection water caused by removing bacteria and contribution rate in reinjection water corrosion by microorganism. The results show that high temperature steam sterilization can remove all the germs, as well as change water chemical property. Through centrifugal degerming, water chemical property remains the same, but germs cannot be completely removed. By filtration sterilization, water chemical property undergoes no change while germs are completely removed. Besides, it can better reflect the role of microorganisms in corrosion. The research results indicate that microorganism is the leading factor of reinjection water corrosion in Ninghai area where the contribution rate is 57% to 72%.