Abstract: A method for the determination of mixedness degree of red mud and limestone by spectrophotometry with 1,10-phenanthroline was developed. The mixture of red mud and limestone was dissolved by hydrochloric acid, and iron content in the sample solution was determined by spectrophotometry with 1,10-phenanthroline. The mass fraction of Fe2O3 in the mixture was calculated and used as a representation of mixedness degree. The results of the study show that the new method provides similar precision and accuracy for the mixedness degree determination with the dichromate titration method with relative errors of about 2%. The new method also provides the advantages of simple operation, more efficiency, environmentfriendly and is in favor of realtime monitoring in production.