The invention relates to a passivator, a metal workpiece, and a passivation treatment method therefor. The passivator is used for the surface pretreatment of the metal workpiece. Based on 100 parts byweight, the passivator comprises the following components by mass contents: 0.2 g/L to 4 g/L of cerous nitrate, 0.01 g/L to 0.3 g/L of borax, 0.01 g/L to 0.1 g/L of ammonium bifluoride, 3 g/L to 20 g/L of phytic acid, and 0.01 g/L to 0.3 g/L of nickelous fluoride. Chromium-containing components are not used in the passivator, so that the passivator is a chromium-free passivator and is suitable for passivation treatment of the metal workpiece. After treatment is carried out by using the passivator, a corrosion-resistant passivation layer that is colorless to light-colored is formed. The product does not contain chromium ions doing hard to the environment, is used for providing a bottom layer for coating treatment and preservative treatment, is a green and environmentally-friendly product;and if magnesium alloy is treated, the PH value is adjusted to 5 to 6 by using ammonia water.