According to Limitation requirements of toxic and harmful substance in fertilizers(GB 38400—2019)and Determination of total nickel，total cobalt，total selenium，total vanadium，totalstibium，total thallium in fertilizers—Inductively coupled plasma optical emission spectroscopy(GB/T 39356—2020)，the content of total nickel，total cobalt，total selenium，total vanadium，total stibium，total thallium in fertilizer were determined by inductively coupled plasma optical emission spectrometer，and the sources of uncertainty in the determination process were analyzed. By establishing a mathematical model and evaluating and quantifying each uncertainty component，the combined uncertainty and expanded uncertainty of the determination results were obtained.