The invention relates to a color comparison testing and analyzing method of cobalt ion. The method uses 8-hydroxyquinoline as electron donor, 7, 7, 8, 8-tetracyanoquinodimethane as electron acceptor. Colored charge transfer complex is formed in polar solvent through the charge transferring effect among molecule and is made as testing reagent. Water-soluble cobalt salt are made into water solution of definite viscosity, a definite volume of water solution and the testing reagent with same volume are mixed. The color of the solution changes obviously, and other metal ion doesn't interfere cobalt ion. With room temperature testing, the color comparison reaction of the testing reagent to cobalt ion can be identified by eyes or tested by using ultraviolet-visible spectrophotometer. The invention has very professional color comparison identifying capability to cobalt ion the preparation of solution is convenient, the operation of the color comparison is very simple, and the color changing speed of color comparison reaction is quick, which can finish the color comparison test to the tested object in very short time.