A matrix layer is often used in the packaging of fiber Bragg grating strain sensors, and the matrix layer’ structure influences the accuracy of the sensor’s strain monitoring of the structure to be measured. In this study, to obtain a better base layer structure, four-dimension parameters (distance from the loop structure to the middle section, middle section’s width, and depth of the groove) are taken as the sensor variables to investigate the effect of dimension parameters on strain sensitivity using finite element simulation. The structure-optimized sensor is built, tested, and the unknown parameters are calibrated to determine the sensor’s sensitivity, precision, and effective measurement range. The sensor is compared with a standard resistance strain sensor, and the subsequent optimization scheme is given.