Milk is the primary source of nutrition for young mammals before they are able to digest other types of food. Milk contains 3.3% total protein. As milk protein contain all 9 essential amino acids required by humans,so we select milk for protein studies. In this paper a novel method and instrumental system is used to determine the total protein concentration in a milk sample. It uses a fiber optic protein sensor based on the principles of fiber optic evanescent wave absorption. The evanescent waves at the fiber optic core-cladding interface are used to monitor the protein-induced changes in the sensor element. This system measures protein concentration in milk sample without destroying the sample. This new approach has the potential to offer significant sensitivity enhancements over more conventional protein sensing technology which may be time consuming or less economical. Keywords:evanescent wave, protein sensor, fiber optic sensor