The samples to be tested are oxidized to hexavalent chromium in different forms and valence states of chromium in the samples to be tested after high-temperature and high-pressure reactions in the presence of alkaline and oxidizing agents. In an acidic solution, hexavalent chromium reacts with a color developer to produce a purplish-red complex. The complex has maximum absorption at a specific wavelength, and the total chromium content in the sample to be tested is calculated by photoelectric colorimetry.