It is essential to study the dynamic behavior of the soil to make clear the characteristics of ground behavior during earthquake. However, the relationship between the dynamic characteristics and the strain of the soil is not completely studied, because there is no device to measure the strain of the real ground directly. Therefore, it is necessary to develop the ground strain measuring system which can be applied to the real ground. This study presents a system to measure the ground strain, using the fiber Bragg grating (FBG) sensors. Using optical fiber sensor makes the devices simple in mechanism and highly durable. We improve the strain measuring device which was proposed by Sato et al. and also develop a new strain measuring device based on a different mechanism. Their applicability is studied in the experiments. The results in the experiment indicate that it is possible to measure the ground strain by the presented systems with the same level of accuracy as that of the systems by Sato et al. It is also important to recognize the necessity to improve the accuracy.