In this work, the bond behaviour between concrete and glass fibre reinforced polymer (GFRP) bars is investigated with distributed fibre optical sensors (DFOSs). With the feature of measuring strain along the bar continuously of DFOS, the strain distributions along GFRP bars in the concrete have been fully measured in the first time. Besides, numerical simulations taking into account the non-linear behaviour of concrete material verified have been carried out to verify the test results. Moreover, a parameter study has been carried out to gain a more comprehensive understanding of the bond performances of GFRP reinforcements.