Abstract: Through establishing image processing and analysis system and using computer digital technology to conduct metallographic microstructure collection, processing, analysis and grain degree evaluation, the traditional metallographic analysis technology and grain degree evaluation method were replaced. The results show that the microstructure image which was collected by this system is much clearer, and grain size rating is more efficient and accurate compared with the traditional method. The system had been applied to the metallographic examination of various X60 and X70 specifications of hot-bending elbows used in Sichuan to East Gas Transmission Pipeline Project, and it can satisfy the metallographic inspection requirements to hot-bending elbows of this project.