Aiming at the problem that the residual strain caused by steel structure welding is difficult to calculate accurately theo- retically， optical fiber calibration test and I-steel welding test are carried out based on optical frequency domain reflectometer(OFDR) technology， and the application of this technology in steel structure welding residual strain monitoring is studied. The test and analysis results show that OFDR technology can accurately monitor the welding residual strain and the location of strain can be precisely located.