Three cylindrical mortar specimens containing 12, 16， 20mm diameter reinforcement steels were fabricated, and optical fiber was wrapped around the mortar cylinder in a spiral mode with a spacing of 100mm. Three specimens were subjected to accelerated corrosion test. Reinforcement steel corrosion was monitored with optical frequency domain reflectometer(OFDR) distributed optical fiber. During the accelerated corrosion test, strain data on the mortar surface induced by reinforcement steel corrosion were collected with OFDR optical fiber. Results show that corrosion of reinforcement steels causes surface cracking of mortar protective layer and results in appearance of strain peaks along the OFDR fiber. The magnitude of strain peak increases with an increase of corrosion induced mass loss of reinforcement steel. At the same corrosion level, thinner protective layer (or bigger reinforcement steel) causes a higher cracking rate and consequently a bigger crack width.