Based on laboratory accumulated quality control data，the top down method can be directly used to evaluate measurement uncertainty，which is more convenient than traditional bottom up methods.Our laboratory accumulated 41 data on the nitrogen content of fertilizer quality control samples determined by the Dumas combustion method.The Anderson-Darling test for normal distribution of data and the t-test for bias from theoretical reference were conducted. Result indicated that the measured data was randomly distributed.The quality control chart according to the average and exponential weighted moving average values confirmed that the measurement system was controlled.The extended measurement uncertainty of 0.24% and 0.26% were calculated using the quality control chart method and robust statistical iteration method，respectively.The measurement uncertainty of the Dumas method for determining fertilizer nitrogen content obtained by the two methods had good consistency.The top down method can be practicality carried out through the quality control data accumulated in the laboratory.Moreover，the evaluation of measurement uncertainty of detection methods is linked with laboratory quality control work.