Abstract: Aiming at the problem that the content of hexavalent chromium in the magnesium chromate coating of non-oriented electrical steel after steam bluing treatment exceeded the standard, the effects of bluing process on the content of hexavalent chromium in the coating of non-oriented electrical steel under different atmospheres were studied by means of ultraviolet-visible spectrophotometer and atmosphere heat treatment. The results show that under the condition of N₂ atmosphere and reducing atmosphere, the content of hexavalent chromium in the coating would decrease with the extension of blueing time and the increase of temperature. However, the content of hexavalent chromium in the coating did not decrease significantly at lower blueing temperature. In order to completely solve the problem of excessive hexavalent chromium content, it was necessary to ensure that the hexavalent chromium content of the coating reached the standard after baking and curing.