In order to measure the change of liquid level near the warning value, a new optical fiber fusion splicer was used to fabricate a fiber optic sensor for measuring liquid level based on long-period fiber grating with tapered structure. The refractive index sensitivity of the liquid level sensing experimental system was built to measure the length of the optical fiber immersed in the liquid. The results show that in the liquid level measurement range of 0 mm~12 mm, the peak wavelength sensitivity and transmission power sensitivity of the optical fiber liquid level sensor were 0.700 nm/mm and 1.377 dB/nm, respectively. The sensor is more accurate in measuring the liquid level change, and the grating method mentioned above can effectively solve the problems of asymmetric mode coupling and high polarization dependence in the traditional long-period fiber grating,and it has the advantages of simplicity, low cost and wide application prospects.