In mathematical bio-sciences we study the applications of mathematical modeling and mathematical techniques to get an insight into the problems of bio-sciences. The mathematical model is a comprehensive process of representing real Phenomena in terms of Mathematical Equations, and extracting from them useful information for understanding and predicting the process of idealization. The study of blood flow characteristics in human circulatory system in the presence of stenosis, has been the subject of researchers in recent years. A serious study of this problem has been done by Young 1968 who presented a mathematical model to analyses theoretically the effects of stenosis on flow characteristics of blood and concluded that the resistance to the flow and the wall shear stress increase with the increase in stenosis size. The blood flow through large arteries considered as Newtonian flow by Lee JS 1974. while the blood flow through small arteries is considered as non-Newtonian by Chan et all 2007.