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• A high-sensitivity, quasi-temperature-insensitive magnetic field sensor is experimentally demonstrated. • Temperature affect induced by thermal expansion is eliminated by the symmetry of optical structure. • Experimental results show that the maximum sensitivity could be 4.36 nm/mT. This paper proposed and experimentally demonstrated a high resolution and quasi-temperature-insensitive magnetic field sensor based on hybrid interferometer. The sensor is created by cascading a Mach Zehnder interferometer (MZI) and a Sagnac loop interferometer (SI). Due to the symmetry of the MZI's two arms, the length change induced by thermal expansion is approximate identical, meaning the temperature perturbation would be eliminated. Moreover, the free spectrum ranges of MZI and SI are extremely close, thus the sensitivity is amplified by the vernier effect. Experiment results indicate that the magnetic field sensitivity of the MZI is 118.8 pm/mT, while the sensitivity of the sensor is 4.36 nm/mT, which is about 36.9 times higher than it in the MZI. [ABSTRACT FROM AUTHOR]