Abstract: Float level meter is widely used in the refining and chemical plate. The XTD-30 series electric float level meter used in a hydrogenation unit has frequent deviation alarm for more than one year, resulting in adjustment failure. The working principle and characteristics of this series of electric float liquid level gauge are studied, and the relevant process conditions, installation scheme of the gauge, liquid level calculation method and precautions are introduced. Combined with the actual use of the field equipment, the investigation on the deviation alarm of the series of float liquid level gauge is carried out, and the influencing factors of the liquid level deviation are analyzed. It is mainly influenced by the change of the density of the measured medium and the sudden change of the ambient temperature. Through the field operation calculation of density and liquid level and the study of liquid level variation trend combined with ambient temperature in the past year, it is concluded that density and temperature will affect the change of liquid level parameters, and it is verified that the main influencing factor of liquid level deviation is the change of density caused by temperature. By adjusting the parameters of the liquid level gauge on site, the range migration improves the stability of the liquid level control, optimizes the heat tracing measures to ensure the stability of the ambient temperature of the liquid level gauge, and maintains stability in subsequent liquid level adjustment. The solution and improvement measures have a guiding effect on the subsequent treatment of similar instrument faults, and provide a new way to solve such problems.