Strain measurement is an important problem in bridge health assessment. Fiber Bragg grating is a kind of optical fiber passive components with wavelength modulation effect, and has small volume, high corrosion resistance, good electrical insulation measurement precision, good stability, short response time, and the advantages of distributed measurement. Along with the development of technology, optical fiber Bragg grating sensor for structural health monitoring, space exploration, power system measurement, medical equipment improvement, and other fields has been widely concerned. However, in the process of monitoring bridge strain, the sensitivity of FBG strain sensor will decrease due to long-time use. The resistance strain gauge has the advantages of high precision, good consistency and good repeatability, and is commonly used as the strain sensor. Therefore, in practical process, the resistance strain gauge can usually be used as the reference sensor and the FIBER Bragg grating strain sensor as the sensor to be calibrated. Therefore, an in-situ calibration method is proposed for the accuracy of fiber Bragg grating strain sensor in measuring bridge structural strain. The resistance strain gauge was used as the reference sensor, and the FIBER Bragg grating strain sensor was used as the sensor to be calibrated. The temperature was kept unchanged to avoid the wavelength drift of the fiber Bragg grating strain sensor caused by temperature change. The cantilever beam with equal strength is used to simulate the bridge structure, and the weight is used as the excitation source to simulate the loading and unloading process of the bridge load. By referring to the strain measurement of the response of the sensor and the sensor to be calibrated, the two sensors are installed in a close position to measure and compare. In the actual bridge measurement process, due to uncontrollable environmental factors affecting the measurement results, abnormal jump points appear in the strain output waveform, which can affect the calibration coefficient generated by the actual data matching results, so it is necessary to remove abnormal jump points. In addition, due to the difference in characteristics of different sensors, there is usually data dislocation between the measured value sequence of the calibrated sensor and the reference value sequence, which makes it impossible to judge the consistency of the strain response of the sensor. Therefore, based on the data sequence matching method of dynamic time warping algorithm, the strain data of resistance strain gauge and fiber grating strain sensor are matched and analyzed, and the data matching rate is above 96%. The results show that the method can effectively solve the problem of whether the strain response of the sensor is consistent, and can realize the in-situ calibration of the FIBER Bragg grating strain sensor, and the in-situ calibration results are basically the same as the static calibration results.