Abstract: Karl Fischer volumetric titrator, which has the characteristic of simple structure and accurate measurement, is widely used in petroleum, chemical industry, food industry and other fields. In order to ensure the accuracy of measurement, the titrator is should be calibrated in accordance with the requirements of the JJG 1154-2018. Taking Karl Fischer volumetric titrator as an example, the matters needing attention in the calibration are discussed in detail, and the uncertainty of relative indication error calibration is evaluated.