The aim of this chapter is to focus on the qualitative analysis of proteins. Proteins are defined as sequence specific polymers of L α-amino acids linked by peptide bonds. They are complex organic substances made up of carbon, hydrogen, oxygen and nitrogen. Some proteins also contain sulfur and phosphorus. Classification of protein, functions of proteins, reactions of proteins, color reactions for proteins, and identification of unknown protein are also discussed. Functions of proteins are maintain the structural integrity of bones, tendons, hair and teeth—collagen, elastin, keratin; acts as enzymes (catalytic function), hormones (regulatory function), Antibodies, Coagulation factors, and contractile element in the muscle (actin, myosin).