According to JJF1059.1-2012 Evaluation and Expression of Measurement Uncertainty and CNAS-GL-06 Evaluation Guide of Uncertainty in Chemical Analysis, a mathematical model for the evaluation of uncertainty in the determination of nitrite in pickled cabbage by spectrophotometer was established. The sources of uncertainty in the process of measurement were analyzed, and the components of uncertainty were calculated, and the relative uncertainty and the expanded uncertainty were synthesized. The results showed that the mean value of nitrite in spectrophotometer was 6.21 mg/kg, the expanded uncertainty was 0.322 mg/kg, and the value was X（6.21±0.322） mg/kg.The main source of uncertainty is the drawing of standard curve. In the process of determining nitrite in pickled cabbage, the correlation coefficient r≥0.997 is selected.