A test method uses for scarcity of blood decorating albumin. It adopts the characteristic that the combining ability is weakening between scarcity of blood decorating albumin and cobalt. It tests the dissociative cobalt in the reaction system with chemistry reagent and shows the content change of dissociative cobalt by change of absorbency to figure the concentration to scarcity of blood decorating albumin indirectly. In testing, the color-developing agent is dithioerythritol for its single configuration, steady character without isomer and the change of test result is small. This can avoid the problem with an unstable test result for the difference of reagent itself, the reagent r producer, reagent species and batch. Displace the absorbency with concentration guideline to the dissociative cobalt in the said test result, to avoid the instability of the test result induced by the capability difference of the apparatus and reagent.