The test results of whether the brewery sludge is suitable for agriculture fertilizer usually needs to consider the uncertainty.The uncertainty of Potassium dichromate titration in brewery sludge was evaluated based on the daily inspection record and the actual testing.The result showed that the uncertainty of measurement was mainly derived from the recovery and repeatability,but not from volume and quantity of the sludge.In addition,reducing the absolute difference between parallel experiments could significantly improve the judgment.Therefore,performing two parallel experiment and spiking standard samples,plus the specific evaluation for each individual case can improve the reliability of the daily testing.