Corrosion causes mass loss of steel bars, concrete cracking, and interface degradation in reinforced concrete, highly compromising the safety and durability of civil infrastructure. This research proposes a smart reinforced concrete instrumented with a distributed fiber optic sensor for in-situ monitoring, presents an innovative method to quantify mass loss of steel bar using unique distributed sensor data, and studies corrosion-induced expansion of steel bar in steel fiber reinforced concrete. Electrochemical test and the distributed sensor data were used to understand the corrosion deterioration process of the steel-concrete composite. Effect of the steel fiber on the deterioration process is evaluated under different concrete surface conditions, and the underlying mechanisms are investigated. The results indicate that steel fibers reduced the corrosion rate of steel bars by mitigating electron transfer from the steel bar, delaying concrete cracking, and limiting the crack width. The effect of concrete surface defects shows a transition phenomenon. This research gains insights into the corrosion deterioration mechanism and strategies for improving the long-term durability of steel-concrete composite.