Objective: The uncertainty of HPLC method for determination of 6-benzyladenine in a soybean sproutswas evaluated by QuEChERS pretreatment method. Methods: A mathematical model was established by analysis of uncertainty sources. Then the individual components of uncertainty were evaluated and the combined uncertainties and expanded uncertainties were calculated. Results: The results showed that the uncertainty caused by serval factors, including the configuration of standard solutions and gradient standard solutions, the fitting of the standard curve, the pretreatment process, the recovery rate and repeatability, and the instrument itself. The content of 6-benzyladenine was 0.335 mg/kg in agricultural products （soybean sprouts）. The relative combined standard uncertainty of the method was about 0.026 mg/kg, k=2. Conclusion: The main sources of uncertainty were the fitting of the standard curve, the configuration of gradient standard solutions and the recovery rate. QuEChERS method can simplify the pretreatment steps and reduce the solvent consumption and the uncertainty of the test.