The samples to be tested were oxidized to tetravalent nickel ions after high temperature and pressure reaction in the presence of oxidant in different forms and valence states. In a strongly alkaline medium, the tetravalent nickel ion reacts with butanedione oxime to form an orange-yellow soluble complex. The complex has maximum absorption at a specific wavelength, and the total nickel content in the sample to be tested was calculated by photoelectric colorimetry.