Abstract: Ultraviolet spectrophotometric method for the evaluation of uncertainty to determine the concentration of oil in seawater.Through analyzing standard solution, standard curve fitting, pretreatment process influencing the results of determination of uncertain degree component, work out the expanded uncertainty, and find out the influence of the uncertain factors.The results show that the UV spectrophotometric method for the determination of oil in seawater concentration uncertainty of the main source is the first process of uncertainty.In this experiment, the uncertainty of oil concentration in seawater is reported as 19.98±1.326 mg/L